diff --git a/test/Makefile.am b/test/Makefile.am
index 847aaad..e510230 100644
--- a/test/Makefile.am
+++ b/test/Makefile.am
@@ -1,4 +1,23 @@
-AM_CPPFLAGS = -I$(top_srcdir) $(CODE_COVERAGE_CPPFLAGS) $(GTEST_CFLAGS)
+COMMON_CXX = \
+    -flto \
+    -Wno-psabi \
+    $(SDBUSPLUS_CFLAGS) \
+    $(SYSTEMD_CFLAGS) \
+    $(libmapper_CFLAGS) \
+    $(SDBUSPLUS_CFLAGS) \
+    $(PHOSPHOR_LOGGING_CFLAGS) \
+    $(PHOSPHOR_DBUS_INTERFACES_CFLAGS) \
+    -DBOOST_ERROR_CODE_HEADER_ONLY \
+    -DBOOST_SYSTEM_NO_DEPRECATED \
+    -DBOOST_COROUTINES_NO_DEPRECATION_WARNING \
+    -DBOOST_ASIO_DISABLE_THREADS \
+    -DBOOST_ALL_NO_LIB
+
+AM_CPPFLAGS = \
+    -I$(top_srcdir) \
+    -I$(top_srcdir)/include \
+    $(CODE_COVERAGE_CPPFLAGS) \
+    $(GTEST_CFLAGS)
 AM_CFLAGS = $(CODE_COVERAGE_CFLAGS)
 AM_CXXFLAGS = $(GTEST_MAIN_CFLAGS) $(GTEST_CFLAGS)
 AM_LDFLAGS = $(GTEST_MAIN_LIBS) $(OESDK_TESTCASE_FLAGS)
@@ -11,7 +30,7 @@
 sample_unittest_CPPFLAGS = -Igtest $(GTEST_CPPFLAGS) $(AM_CPPFLAGS)
 sample_unittest_CXXFLAGS = $(PTHREAD_CFLAGS) $(CODE_COVERAGE_CXXFLAGS) \
 			   $(CODE_COVERAGE_CFLAGS)
-sample_unittest_LDFLAGS = -lgtest_main -lgtest $(PTHREAD_LIBS) $(OESDK_TESTCASE_FLAGS) \
+sample_unittest_LDFLAGS = -lgtest_main -lgtest -pthread $(OESDK_TESTCASE_FLAGS) \
    			$(CODE_COVERAGE_LDFLAGS)
 sample_unittest_SOURCES = %reldir%/sample_unittest.cpp
 sample_unittest_LDADD = $(top_builddir)/sample.o
@@ -22,3 +41,29 @@
 #check_PROGRAMS += oemrouter_unittest
 #oemrouter_unittest_SOURCES = oemrouter_unittest.cpp
 #oemrouter_unittest_LDADD = $(top_builddir)/oemrouter.o
+
+# Build/add message packing/unpacking unit tests
+message_unittest_CPPFLAGS = \
+    -Igtest \
+    $(GTEST_CPPFLAGS) \
+    $(AM_CPPFLAGS)
+message_unittest_CXXFLAGS = \
+    $(COMMON_CXX) \
+    $(PTHREAD_CFLAGS) \
+    $(PHOSPHOR_LOGGING_CFLAGS) \
+    $(CODE_COVERAGE_CXXFLAGS) \
+    $(CODE_COVERAGE_CFLAGS)
+message_unittest_LDFLAGS = \
+    -lgtest_main \
+    -lgtest \
+    -lsdbusplus \
+    -lsystemd \
+    -pthread \
+    $(PHOSPHOR_LOGGING_LIBS) \
+    $(OESDK_TESTCASE_FLAGS) \
+    $(CODE_COVERAGE_LDFLAGS)
+message_unittest_SOURCES = \
+    %reldir%/message/payload.cpp \
+    %reldir%/message/unpack.cpp \
+    %reldir%/message/pack.cpp
+check_PROGRAMS += %reldir%/message_unittest
diff --git a/test/message/pack.cpp b/test/message/pack.cpp
new file mode 100644
index 0000000..60459ed
--- /dev/null
+++ b/test/message/pack.cpp
@@ -0,0 +1,324 @@
+/**
+ * Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <ipmid/api.hpp>
+#include <ipmid/message.hpp>
+
+#include <gtest/gtest.h>
+
+// TODO: Add testing of Payload response API
+
+TEST(PackBasics, Uint8)
+{
+    ipmi::message::Payload p;
+    uint8_t v = 4;
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x04};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Uint16)
+{
+    ipmi::message::Payload p;
+    uint16_t v = 0x8604;
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x04, 0x86};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Uint32)
+{
+    ipmi::message::Payload p;
+    uint32_t v = 0x02008604;
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x04, 0x86, 0x00, 0x02};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Uint64)
+{
+    ipmi::message::Payload p;
+    uint64_t v = 0x1122334402008604ull;
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x04, 0x86, 0x00, 0x02, 0x44, 0x33, 0x22, 0x11};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Uint24)
+{
+    ipmi::message::Payload p;
+    uint24_t v = 0x112358;
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), types::nrFixedBits<decltype(v)> / CHAR_BIT);
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x58, 0x23, 0x11};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Uint3Uint5)
+{
+    // individual bytes are packed low-order-bits first
+    // v1 will occupy [2:0], v2 will occupy [7:3]
+    ipmi::message::Payload p;
+    uint3_t v1 = 0x1;
+    uint5_t v2 = 0x19;
+    p.pack(v1, v2);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), (types::nrFixedBits<decltype(v1)> +
+                         types::nrFixedBits<decltype(v2)>) /
+                            CHAR_BIT);
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0xc9};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Boolx8)
+{
+    // individual bytes are packed low-order-bits first
+    // [v8, v7, v6, v5, v4, v3, v2, v1]
+    ipmi::message::Payload p;
+    bool v8 = true, v7 = true, v6 = false, v5 = false;
+    bool v4 = true, v3 = false, v2 = false, v1 = true;
+    p.pack(v1, v2, v3, v4, v5, v6, v7, v8);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(uint8_t));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0xc9};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Bitset8)
+{
+    // individual bytes are packed low-order-bits first
+    // a bitset for 8 bits fills the full byte
+    ipmi::message::Payload p;
+    std::bitset<8> v(0xc9);
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() / CHAR_BIT);
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0xc9};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Bitset3Bitset5)
+{
+    // individual bytes are packed low-order-bits first
+    // v1 will occupy [2:0], v2 will occupy [7:3]
+    ipmi::message::Payload p;
+    std::bitset<3> v1(0x1);
+    std::bitset<5> v2(0x19);
+    p.pack(v1, v2);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), (v1.size() + v2.size()) / CHAR_BIT);
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0xc9};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Bitset32)
+{
+    // individual bytes are packed low-order-bits first
+    // v1 will occupy 4 bytes, but in LSByte first order
+    // v1[7:0] v1[15:9] v1[23:16] v1[31:24]
+    ipmi::message::Payload p;
+    std::bitset<32> v(0x02008604);
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() / CHAR_BIT);
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x04, 0x86, 0x00, 0x02};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Array4xUint8)
+{
+    // an array of bytes will be output verbatim, low-order element first
+    ipmi::message::Payload p;
+    std::array<uint8_t, 4> v = {{0x02, 0x00, 0x86, 0x04}};
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() * sizeof(v[0]));
+    // check that the bytes were correctly packed (in byte order)
+    std::vector<uint8_t> k = {0x02, 0x00, 0x86, 0x04};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, Array4xUint32)
+{
+    // an array of multi-byte values will be output in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    ipmi::message::Payload p;
+    std::array<uint32_t, 4> v = {
+        {0x11223344, 0x22446688, 0x33557799, 0x12345678}};
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() * sizeof(v[0]));
+    // check that the bytes were correctly packed (in byte order)
+    std::vector<uint8_t> k = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34, 0x12};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, VectorUint32)
+{
+    // a vector of multi-byte values will be output in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    ipmi::message::Payload p;
+    std::vector<uint32_t> v = {
+        {0x11223344, 0x22446688, 0x33557799, 0x12345678}};
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() * sizeof(v[0]));
+    // check that the bytes were correctly packed (in byte order)
+    std::vector<uint8_t> k = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34, 0x12};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackBasics, VectorUint8)
+{
+    // a vector of bytes will be output verbatim, low-order element first
+    ipmi::message::Payload p;
+    std::vector<uint8_t> v = {0x02, 0x00, 0x86, 0x04};
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), v.size() * sizeof(v[0]));
+    // check that the bytes were correctly packed (in byte order)
+    std::vector<uint8_t> k = {0x02, 0x00, 0x86, 0x04};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackAdvanced, Uints)
+{
+    // all elements will be processed in order, with each multi-byte
+    // element being processed LSByte first
+    // v1[7:0] v2[7:0] v2[15:8] v3[7:0] v3[15:8] v3[23:16] v3[31:24]
+    // v4[7:0] v4[15:8] v4[23:16] v4[31:24]
+    // v4[39:25] v4[47:40] v4[55:48] v4[63:56]
+    ipmi::message::Payload p;
+    uint8_t v1 = 0x02;
+    uint16_t v2 = 0x0604;
+    uint32_t v3 = 0x44332211;
+    uint64_t v4 = 0xccbbaa9988776655ull;
+    p.pack(v1, v2, v3, v4);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v1) + sizeof(v2) + sizeof(v3) + sizeof(v4));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x02, 0x04, 0x06, 0x11, 0x22, 0x33, 0x44, 0x55,
+                              0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackAdvanced, TupleInts)
+{
+    // all elements will be processed in order, with each multi-byte
+    // element being processed LSByte first
+    // v1[7:0] v2[7:0] v2[15:8] v3[7:0] v3[15:8] v3[23:16] v3[31:24]
+    // v4[7:0] v4[15:8] v4[23:16] v4[31:24]
+    // v4[39:25] v4[47:40] v4[55:48] v4[63:56]
+    ipmi::message::Payload p;
+    uint8_t v1 = 0x02;
+    uint16_t v2 = 0x0604;
+    uint32_t v3 = 0x44332211;
+    uint64_t v4 = 0xccbbaa9988776655ull;
+    auto v = std::make_tuple(v1, v2, v3, v4);
+    p.pack(v);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(v1) + sizeof(v2) + sizeof(v3) + sizeof(v4));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x02, 0x04, 0x06, 0x11, 0x22, 0x33, 0x44, 0x55,
+                              0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackAdvanced, BoolsnBitfieldsnFixedIntsOhMy)
+{
+    // each element will be added, filling the low-order bits first
+    // with multi-byte values getting added LSByte first
+    // v1 will occupy k[0][1:0]
+    // v2 will occupy k[0][2]
+    // v3[4:0] will occupy k[0][7:3], v3[6:5] will occupy k[1][1:0]
+    // v4 will occupy k[1][2]
+    // v5 will occupy k[1][7:3]
+    ipmi::message::Payload p;
+    uint2_t v1 = 2;          // binary 0b10
+    bool v2 = true;          // binary 0b1
+    std::bitset<7> v3(0x73); // binary 0b1110011
+    bool v4 = false;         // binary 0b0
+    uint5_t v5 = 27;         // binary 0b11011
+    // concat binary: 0b1101101110011110 -> 0xdb9e -> 0x9e 0xdb (LSByte first)
+    p.pack(v1, v2, v3, v4, v5);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(uint16_t));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x9e, 0xdb};
+    ASSERT_EQ(p.raw, k);
+}
+
+TEST(PackAdvanced, UnalignedBitPacking)
+{
+    // unaligned multi-byte values will be packed the same as
+    // other bits, effectively building up a large value, low-order
+    // bits first, then outputting a stream of LSByte values
+    // v1 will occupy k[0][1:0]
+    // v2[5:0] will occupy k[0][7:2], v2[7:6] will occupy k[1][1:0]
+    // v3 will occupy k[1][2]
+    // v4[4:0] will occupy k[1][7:3] v4[12:5] will occupy k[2][7:0]
+    // v4[15:13] will occupy k[3][2:0]
+    // v5 will occupy k[3][3]
+    // v6[3:0] will occupy k[3][7:0] v6[11:4] will occupy k[4][7:0]
+    // v6[19:12] will occupy k[5][7:0] v6[27:20] will occupy k[6][7:0]
+    // v6[31:28] will occupy k[7][3:0]
+    // v7 will occupy k[7][7:4]
+    ipmi::message::Payload p;
+    uint2_t v1 = 2;           // binary 0b10
+    uint8_t v2 = 0xa5;        // binary 0b10100101
+    bool v3 = false;          // binary 0b0
+    uint16_t v4 = 0xa55a;     // binary 0b1010010101011010
+    bool v5 = true;           // binary 0b1
+    uint32_t v6 = 0xdbc3bd3c; // binary 0b11011011110000111011110100111100
+    uint4_t v7 = 9;           // binary 0b1001
+    // concat binary:
+    //   0b1001110110111100001110111101001111001101001010101101001010010110
+    //   -> 0x9dbc3bd3cd2ad296 -> 0x96 0xd2 0x2a 0xcd 0xd3 0x3b 0xbc 0x9d
+    p.pack(v1, v2, v3, v4, v5, v6, v7);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.size(), sizeof(uint64_t));
+    // check that the bytes were correctly packed (LSB first)
+    std::vector<uint8_t> k = {0x96, 0xd2, 0x2a, 0xcd, 0xd3, 0x3b, 0xbc, 0x9d};
+    ASSERT_EQ(p.raw, k);
+}
diff --git a/test/message/payload.cpp b/test/message/payload.cpp
new file mode 100644
index 0000000..9d20ff0
--- /dev/null
+++ b/test/message/payload.cpp
@@ -0,0 +1,308 @@
+/**
+ * Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <ipmid/api.hpp>
+#include <ipmid/message.hpp>
+
+#include <gtest/gtest.h>
+
+TEST(Payload, InputSize)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    size_t input_size = i.size();
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    ASSERT_EQ(input_size, p.size());
+}
+
+TEST(Payload, OutputSize)
+{
+    ipmi::message::Payload p;
+    ASSERT_EQ(0, p.size());
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    p.pack(i);
+    ASSERT_EQ(i.size(), p.size());
+    p.pack(i);
+    p.pack(i);
+    ASSERT_EQ(3 * i.size(), p.size());
+}
+
+TEST(Payload, Resize)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p;
+    p.pack(i);
+    p.resize(16);
+    ASSERT_EQ(p.size(), 16);
+}
+
+TEST(Payload, Data)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p;
+    p.pack(i);
+    ASSERT_NE(nullptr, p.data());
+}
+
+TEST(PayloadResponse, Append)
+{
+    std::string s("0123456789abcdef");
+    ipmi::message::Payload p;
+    p.append(s.data(), s.data() + s.size());
+    ASSERT_EQ(s.size(), p.size());
+}
+
+TEST(PayloadResponse, AppendDrain)
+{
+    std::string s("0123456789abcdef");
+    ipmi::message::Payload p;
+    bool b = true;
+    // first pack a lone bit
+    p.pack(b);
+    p.append(s.data(), s.data() + s.size());
+    // append will 'drain' first, padding the lone bit into a full byte
+    ASSERT_EQ(s.size() + 1, p.size());
+}
+
+TEST(PayloadResponse, AppendBits)
+{
+    ipmi::message::Payload p;
+    p.appendBits(3, 0b101);
+    ASSERT_EQ(p.bitStream, 0b101);
+    p.appendBits(4, 0b1100);
+    ASSERT_EQ(p.bitStream, 0b1100101);
+    p.appendBits(1, 0b1);
+    ASSERT_EQ(p.bitStream, 0);
+    ASSERT_EQ(p.bitCount, 0);
+    // appended 8 bits, should be one byte
+    ASSERT_EQ(p.size(), 1);
+    std::vector<uint8_t> k1 = {0b11100101};
+    ASSERT_EQ(p.raw, k1);
+    p.appendBits(7, 0b1110111);
+    // appended 7 more bits, should still be one byte
+    ASSERT_EQ(p.size(), 1);
+    p.drain();
+    // drain forces padding; should be two bytes now
+    ASSERT_EQ(p.size(), 2);
+    std::vector<uint8_t> k2 = {0b11100101, 0b01110111};
+    ASSERT_EQ(p.raw, k2);
+}
+
+TEST(PayloadResponse, Drain16Bits)
+{
+    ipmi::message::Payload p;
+    p.bitStream = 0b1011010011001111;
+    p.bitCount = 16;
+    p.drain();
+    ASSERT_EQ(p.size(), 2);
+    ASSERT_EQ(p.bitCount, 0);
+    ASSERT_EQ(p.bitStream, 0);
+    std::vector<uint8_t> k1 = {0b11001111, 0b10110100};
+    ASSERT_EQ(p.raw, k1);
+}
+
+TEST(PayloadResponse, Drain15Bits)
+{
+    ipmi::message::Payload p;
+    p.bitStream = 0b101101001100111;
+    p.bitCount = 15;
+    p.drain();
+    ASSERT_EQ(p.size(), 2);
+    ASSERT_EQ(p.bitCount, 0);
+    ASSERT_EQ(p.bitStream, 0);
+    std::vector<uint8_t> k1 = {0b1100111, 0b1011010};
+    ASSERT_EQ(p.raw, k1);
+}
+
+TEST(PayloadResponse, Drain15BitsWholeBytesOnly)
+{
+    ipmi::message::Payload p;
+    p.bitStream = 0b101101001100111;
+    p.bitCount = 15;
+    p.drain(true);
+    // only the first whole byte should have been 'drained' into p.raw
+    ASSERT_EQ(p.size(), 1);
+    ASSERT_EQ(p.bitCount, 7);
+    ASSERT_EQ(p.bitStream, 0b1011010);
+    std::vector<uint8_t> k1 = {0b1100111};
+    ASSERT_EQ(p.raw, k1);
+}
+
+TEST(PayloadRequest, Pop)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    const auto& [vb, ve] = p.pop<uint8_t>(4);
+    std::vector<uint8_t> v(vb, ve);
+    std::vector<uint8_t> k = {0xbf, 0x04, 0x86, 0x00};
+    ASSERT_EQ(v, k);
+}
+
+TEST(PayloadRequest, FillBits)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(5);
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0xbf);
+    ASSERT_EQ(p.bitCount, 8);
+    // should still have 5 bits available, no change
+    p.fillBits(5);
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0xbf);
+    ASSERT_EQ(p.bitCount, 8);
+    // discard 5 bits (low order)
+    p.popBits(5);
+    // should add another byte into the stream (high order)
+    p.fillBits(5);
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0x25);
+    ASSERT_EQ(p.bitCount, 11);
+}
+
+TEST(PayloadRequest, FillBitsTooManyBits)
+{
+    std::vector<uint8_t> i = {1, 2, 3, 4, 5, 6, 7, 8, 9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(72);
+    ASSERT_TRUE(p.unpackError);
+}
+
+TEST(PayloadRequest, FillBitsNotEnoughBytes)
+{
+    std::vector<uint8_t> i = {1, 2, 3, 4};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(48);
+    ASSERT_TRUE(p.unpackError);
+}
+
+TEST(PayloadRequest, PopBits)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(4);
+    uint8_t v = p.popBits(4);
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0x0b);
+    ASSERT_EQ(p.bitCount, 4);
+    ASSERT_EQ(v, 0x0f);
+}
+
+TEST(PayloadRequest, PopBitsNoFillBits)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.popBits(4);
+    ASSERT_TRUE(p.unpackError);
+}
+
+TEST(PayloadRequest, DiscardBits)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(5);
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0xbf);
+    ASSERT_EQ(p.bitCount, 8);
+    p.discardBits();
+    ASSERT_FALSE(p.unpackError);
+    ASSERT_EQ(p.bitStream, 0);
+    ASSERT_EQ(p.bitCount, 0);
+}
+
+TEST(PayloadRequest, FullyUnpacked)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint32_t v1;
+    p.unpack(v1);
+    // still one remaining byte
+    ASSERT_FALSE(p.fullyUnpacked());
+    p.fillBits(3);
+    p.popBits(3);
+    // still five remaining bits
+    ASSERT_FALSE(p.fullyUnpacked());
+    p.fillBits(5);
+    p.popBits(5);
+    // fully unpacked, should be no errors
+    ASSERT_TRUE(p.fullyUnpacked());
+    p.fillBits(4);
+    // fullyUnpacked fails because an attempt to unpack too many bytes
+    ASSERT_FALSE(p.fullyUnpacked());
+}
+
+TEST(PayloadRequest, ResetInternal)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    p.fillBits(4);
+    p.unpackError = true;
+    p.reset();
+    ASSERT_EQ(p.rawIndex, 0);
+    ASSERT_EQ(p.bitStream, 0);
+    ASSERT_EQ(p.bitCount, 0);
+    ASSERT_FALSE(p.unpackError);
+}
+
+TEST(PayloadRequest, ResetUsage)
+{
+    // Payload.reset is used to rewind the unpacking to the initial
+    // state. This is needed so that OEM commands can unpack the group
+    // number or the IANA to determine which handler needs to be called
+    std::vector<uint8_t> i = {0x04, 0x86};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v1;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint8_t k1 = 0x04;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    // do a reset on the payload
+    p.reset();
+    // unpack a uint16
+    uint16_t v2;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v2), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint16_t k2 = 0x8604;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v2, k2);
+}
+
+TEST(PayloadRequest, PartialPayload)
+{
+    std::vector<uint8_t> i = {0xbf, 0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v1;
+    ipmi::message::Payload localPayload;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, localPayload), 0);
+    // check that the payload was partially unpacked and not in error
+    ASSERT_FALSE(p.fullyUnpacked());
+    ASSERT_FALSE(p.unpackError);
+    // check that the 'extracted' payload is not fully unpacked
+    ASSERT_FALSE(localPayload.fullyUnpacked());
+    uint8_t k1 = 0xbf;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    uint32_t v2;
+    // unpack using the 'extracted' payload
+    ASSERT_EQ(localPayload.unpack(v2), 0);
+    ASSERT_TRUE(localPayload.fullyUnpacked());
+    uint32_t k2 = 0x02008604;
+    ASSERT_EQ(v2, k2);
+}
diff --git a/test/message/unpack.cpp b/test/message/unpack.cpp
new file mode 100644
index 0000000..611a5fe
--- /dev/null
+++ b/test/message/unpack.cpp
@@ -0,0 +1,857 @@
+/**
+ * Copyright © 2018 Intel Corporation
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+#include <ipmid/api.hpp>
+#include <ipmid/message.hpp>
+
+#include <gtest/gtest.h>
+
+TEST(Uints, Uint8)
+{
+    std::vector<uint8_t> i = {0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint8_t k = 0x04;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint8TooManyBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint8_t k = 0x04;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint8InsufficientBytes)
+{
+    std::vector<uint8_t> i = {};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v = 0;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(Uints, Uint16)
+{
+    std::vector<uint8_t> i = {0x04, 0x86};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint16_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint16_t k = 0x8604;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint16TooManyBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint16_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint16_t k = 0x8604;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint16InsufficientBytes)
+{
+    std::vector<uint8_t> i = {0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint16_t v = 0;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(Uints, Uint32)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00, 0x02};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint32_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint32_t k = 0x02008604;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint32TooManyBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00, 0x02, 0x44};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint32_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint32_t k = 0x02008604;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint32InsufficientBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint32_t v = 0;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(Uints, Uint64)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00, 0x02, 0x44, 0x33, 0x22, 0x11};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint64_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint64_t k = 0x1122334402008604ull;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint64TooManyBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00, 0x02, 0x44,
+                              0x33, 0x22, 0x11, 0x55};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint64_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint64_t k = 0x1122334402008604ull;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Uints, Uint64InsufficientBytes)
+{
+    std::vector<uint8_t> i = {0x04, 0x86, 0x00, 0x02, 0x44, 0x33, 0x22};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint64_t v = 0;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(Uints, Uint24)
+{
+    std::vector<uint8_t> i = {0x58, 0x23, 0x11};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint24_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint24_t k = 0x112358;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(FixedInts, Uint24TooManyBytes)
+{
+    std::vector<uint8_t> i = {0x58, 0x23, 0x11, 0x00};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint24_t v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint24_t k = 0x112358;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(FixedInts, Uint24InsufficientBytes)
+{
+    std::vector<uint8_t> i = {0x58, 0x23};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint24_t v = 0;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(FixedInts, Uint3Uint5)
+{
+    // individual bytes are unpacked low-order-bits first
+    // v1 will use [2:0], v2 will use [7:3]
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint3_t v1;
+    uint5_t v2;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint3_t k1 = 0x1;
+    uint5_t k2 = 0x19;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+}
+
+TEST(FixedInts, Uint3Uint4TooManyBits)
+{
+    // high order bit should not get unpacked
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint3_t v1;
+    uint4_t v2;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint3_t k1 = 0x1;
+    uint4_t k2 = 0x9;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+}
+
+TEST(FixedInts, Uint3Uint6InsufficientBits)
+{
+    // insufficient bits to unpack v2
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint3_t v1;
+    uint6_t v2;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v1, v2), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    uint3_t k1 = 0x1;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    // check that v2 is zero
+    ASSERT_EQ(v2, 0);
+}
+
+TEST(Bools, Boolx8)
+{
+    // individual bytes are unpacked low-order-bits first
+    // [v8, v7, v6, v5, v4, v3, v2, v1]
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    bool v8, v7, v6, v5;
+    bool v4, v3, v2, v1;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2, v3, v4, v5, v6, v7, v8), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    // check that the bytes were correctly unpacked (LSB first)
+    bool k8 = true, k7 = true, k6 = false, k5 = false;
+    bool k4 = true, k3 = false, k2 = false, k1 = true;
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+    ASSERT_EQ(v5, k5);
+    ASSERT_EQ(v6, k6);
+    ASSERT_EQ(v7, k7);
+    ASSERT_EQ(v8, k8);
+}
+
+TEST(Bools, Boolx8TooManyBits)
+{
+    // high order bit should not get unpacked
+    // individual bytes are unpacked low-order-bits first
+    // [v7, v6, v5, v4, v3, v2, v1]
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    bool v7, v6, v5;
+    bool v4, v3, v2, v1;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2, v3, v4, v5, v6, v7), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that the bytes were correctly unpacked (LSB first)
+    bool k7 = true, k6 = false, k5 = false;
+    bool k4 = true, k3 = false, k2 = false, k1 = true;
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+    ASSERT_EQ(v5, k5);
+    ASSERT_EQ(v6, k6);
+    ASSERT_EQ(v7, k7);
+}
+
+TEST(Bools, Boolx8InsufficientBits)
+{
+    // individual bytes are unpacked low-order-bits first
+    // [v8, v7, v6, v5, v4, v3, v2, v1]
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    bool v9;
+    bool v8, v7, v6, v5;
+    bool v4, v3, v2, v1;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v1, v2, v3, v4, v5, v6, v7, v8, v9), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    // check that the bytes were correctly unpacked (LSB first)
+    bool k8 = true, k7 = true, k6 = false, k5 = false;
+    bool k4 = true, k3 = false, k2 = false, k1 = true;
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+    ASSERT_EQ(v5, k5);
+    ASSERT_EQ(v6, k6);
+    ASSERT_EQ(v7, k7);
+    ASSERT_EQ(v8, k8);
+}
+
+TEST(Bitsets, Bitset8)
+{
+    // individual bytes are unpacked low-order-bits first
+    // a bitset for 8 bits fills the full byte
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<8> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::bitset<8> k(0xc9);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Bitsets, Bitset7TooManyBits)
+{
+    // individual bytes are unpacked low-order-bits first
+    // a bitset for 8 bits fills the full byte
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<7> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<7> k(0x49);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Bitsets, Bitset9InsufficientBits)
+{
+    // individual bytes are unpacked low-order-bits first
+    // a bitset for 8 bits fills the full byte
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<9> v;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<9> k(0);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Bitsets, Bitset3Bitset5)
+{
+    // individual bytes are unpacked low-order-bits first
+    // v1 will use [2:0], v2 will use [7:3]
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<3> v1;
+    std::bitset<5> v2;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::bitset<3> k1(0x1);
+    std::bitset<5> k2(0x19);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+}
+
+TEST(Bitsets, Bitset3Bitset4TooManyBits)
+{
+    // high order bit should not get unpacked
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<3> v1;
+    std::bitset<4> v2;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<3> k1 = 0x1;
+    std::bitset<4> k2 = 0x9;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+}
+
+TEST(Bitsets, Bitset3Bitset6InsufficientBits)
+{
+    // insufficient bits to unpack v2
+    std::vector<uint8_t> i = {0xc9};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<3> v1;
+    std::bitset<6> v2;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v1, v2), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<3> k1 = 0x1;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    // check that v2 is zero
+    ASSERT_EQ(v2, 0);
+}
+
+TEST(Bitsets, Bitset32)
+{
+    // individual bytes are unpacked low-order-bits first
+    // v1 will use 4 bytes, but in LSByte first order
+    // v1[7:0] v1[15:9] v1[23:16] v1[31:24]
+    std::vector<uint8_t> i = {0xb4, 0x86, 0x91, 0xc2};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<32> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::bitset<32> k(0xc29186b4);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Bitsets, Bitset31TooManyBits)
+{
+    // high order bit should not get unpacked
+    std::vector<uint8_t> i = {0xb4, 0x86, 0x91, 0xc2};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<31> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<31> k(0x429186b4);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Bitsets, Bitset33InsufficientBits)
+{
+    // insufficient bits to unpack v2
+    std::vector<uint8_t> i = {0xb4, 0x86, 0x91, 0xc2};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::bitset<33> v;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked (comprehends unpack errors)
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::bitset<33> k(0);
+    // check that v is zero
+    ASSERT_EQ(v, 0);
+}
+
+TEST(Arrays, Array4xUint8)
+{
+    // an array of bytes will be read verbatim, low-order element first
+    std::vector<uint8_t> i = {0x02, 0x00, 0x86, 0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint8_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::array<uint8_t, 4> k = {{0x02, 0x00, 0x86, 0x04}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Arrays, Array4xUint8TooManyBytes)
+{
+    // last byte should not get unpacked
+    // an array of bytes will be read verbatim, low-order element first
+    std::vector<uint8_t> i = {0x02, 0x00, 0x86, 0x04, 0x22};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint8_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::array<uint8_t, 4> k = {{0x02, 0x00, 0x86, 0x04}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Arrays, Array4xUint8InsufficientBytes)
+{
+    // last byte should not get unpacked
+    // an array of bytes will be read verbatim, low-order element first
+    std::vector<uint8_t> i = {0x02, 0x00, 0x86};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint8_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    // arrays of uint8_t will be unpacked all at once
+    // so nothing will get unpacked
+    std::array<uint8_t, 4> k = {{0, 0, 0, 0}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Arrays, Array4xUint32)
+{
+    // an array of multi-byte values will be unpacked in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    std::vector<uint8_t> i = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34, 0x12};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint32_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::array<uint32_t, 4> k = {
+        {0x11223344, 0x22446688, 0x33557799, 0x12345678}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Arrays, Array4xUint32TooManyBytes)
+{
+    // last byte should not get unpacked
+    // an array of multi-byte values will be unpacked in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    std::vector<uint8_t> i = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66,
+                              0x44, 0x22, 0x99, 0x77, 0x55, 0x33,
+                              0x78, 0x56, 0x34, 0x12, 0xaa};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint32_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::array<uint32_t, 4> k = {
+        {0x11223344, 0x22446688, 0x33557799, 0x12345678}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Arrays, Array4xUint32InsufficientBytes)
+{
+    // last value should not get unpacked
+    // an array of multi-byte values will be unpacked in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    std::vector<uint8_t> i = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::array<uint32_t, 4> v;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    // arrays of uint32_t will be unpacked in a way that looks atomic
+    std::array<uint32_t, 4> k = {{0, 0, 0, 0}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Vectors, VectorUint32)
+{
+    // a vector of multi-byte values will be unpacked in order low-order
+    // element first, each multi-byte element in LSByte order
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    std::vector<uint8_t> i = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34, 0x12};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::vector<uint32_t> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::vector<uint32_t> k = {0x11223344, 0x22446688, 0x33557799, 0x12345678};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+// combination of TooManyBytes and InsufficientBytes because
+// vectors will attempt to unpack full <T>s until the end of the input
+TEST(Vectors, VectorUint32NonIntegralBytes)
+{
+    // last value should not get unpacked
+    // a vector of multi-byte values will be unpacked in order low-order
+    // element first, each multi-byte element in LSByte order,
+    // and will attempt to consume all bytes remaining
+    // v[0][7:0] v[0][15:9] v[0][23:16] v[0][31:24]
+    // v[1][7:0] v[1][15:9] v[1][23:16] v[1][31:24]
+    // v[2][7:0] v[2][15:9] v[2][23:16] v[2][31:24]
+    // v[3][7:0] v[3][15:9] v[3][23:16] v[3][31:24]
+    std::vector<uint8_t> i = {0x44, 0x33, 0x22, 0x11, 0x88, 0x66, 0x44, 0x22,
+                              0x99, 0x77, 0x55, 0x33, 0x78, 0x56, 0x34};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::vector<uint32_t> v;
+    // check that the number of bytes matches
+    ASSERT_NE(p.unpack(v), 0);
+    // check that the payload was not fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    // arrays of uint32_t will be unpacked one at a time, so the
+    // last entry should not get unpacked properly
+    std::vector<uint32_t> k = {0x11223344, 0x22446688, 0x33557799};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(Vectors, VectorUint8)
+{
+    // a vector of bytes will be unpacked verbatim, low-order element first
+    std::vector<uint8_t> i = {0x02, 0x00, 0x86, 0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::vector<uint8_t> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::vector<uint8_t> k = {0x02, 0x00, 0x86, 0x04};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+// Cannot test TooManyBytes or InsufficientBytes for vector<uint8_t>
+// because it will always unpack whatever bytes are remaining
+// TEST(Vectors, VectorUint8TooManyBytes) {}
+// TEST(Vectors, VectorUint8InsufficientBytes) {}
+
+TEST(UnpackAdvanced, OptionalOk)
+{
+    // a vector of bytes will be unpacked verbatim, low-order element first
+    std::vector<uint8_t> i = {0xbe, 0x02, 0x00, 0x86, 0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::optional<std::tuple<uint8_t, uint32_t>> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    std::optional<std::tuple<uint8_t, uint32_t>> k{{0xbe, 0x04860002}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(UnpackAdvanced, OptionalInsufficientBytes)
+{
+    // a vector of bytes will be unpacked verbatim, low-order element first
+    std::vector<uint8_t> i = {0x02, 0x00, 0x86, 0x04};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    std::optional<std::tuple<uint8_t, uint32_t>> v;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_FALSE(p.fullyUnpacked());
+    std::optional<std::tuple<uint8_t, uint32_t>> k = {{0, 0}};
+    // check that the bytes were correctly unpacked (in byte order)
+    ASSERT_EQ(v, k);
+}
+
+TEST(UnpackAdvanced, Uints)
+{
+    // all elements will be unpacked in order, with each multi-byte
+    // element being processed LSByte first
+    // v1[7:0] v2[7:0] v2[15:8] v3[7:0] v3[15:8] v3[23:16] v3[31:24]
+    // v4[7:0] v4[15:8] v4[23:16] v4[31:24]
+    // v4[39:25] v4[47:40] v4[55:48] v4[63:56]
+    std::vector<uint8_t> i = {0x02, 0x04, 0x06, 0x11, 0x22, 0x33, 0x44, 0x55,
+                              0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v1;
+    uint16_t v2;
+    uint32_t v3;
+    uint64_t v4;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2, v3, v4), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint8_t k1 = 0x02;
+    uint16_t k2 = 0x0604;
+    uint32_t k3 = 0x44332211;
+    uint64_t k4 = 0xccbbaa9988776655ull;
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+}
+
+TEST(UnpackAdvanced, TupleInts)
+{
+    // all elements will be unpacked in order, with each multi-byte
+    // element being processed LSByte first
+    // v1[7:0] v2[7:0] v2[15:8] v3[7:0] v3[15:8] v3[23:16] v3[31:24]
+    // v4[7:0] v4[15:8] v4[23:16] v4[31:24]
+    // v4[39:25] v4[47:40] v4[55:48] v4[63:56]
+    std::vector<uint8_t> i = {0x02, 0x04, 0x06, 0x11, 0x22, 0x33, 0x44, 0x55,
+                              0x66, 0x77, 0x88, 0x99, 0xaa, 0xbb, 0xcc};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint8_t v1;
+    uint16_t v2;
+    uint32_t v3;
+    uint64_t v4;
+    auto v = std::make_tuple(v1, v2, v3, v4);
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint8_t k1 = 0x02;
+    uint16_t k2 = 0x0604;
+    uint32_t k3 = 0x44332211;
+    uint64_t k4 = 0xccbbaa9988776655ull;
+    auto k = std::make_tuple(k1, k2, k3, k4);
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v, k);
+}
+
+TEST(UnpackAdvanced, BoolsnBitfieldsnFixedIntsOhMy)
+{
+    // each element will be unpacked, filling the low-order bits first
+    // with multi-byte values getting unpacked LSByte first
+    // v1 will use k[0][1:0]
+    // v2 will use k[0][2]
+    // v3[4:0] will use k[0][7:3], v3[6:5] will use k[1][1:0]
+    // v4 will use k[1][2]
+    // v5 will use k[1][7:3]
+    std::vector<uint8_t> i = {0x9e, 0xdb};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint2_t v1;
+    bool v2;
+    std::bitset<7> v3;
+    bool v4;
+    uint5_t v5;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2, v3, v4, v5), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint2_t k1 = 2;          // binary 0b10
+    bool k2 = true;          // binary 0b1
+    std::bitset<7> k3(0x73); // binary 0b1110011
+    bool k4 = false;         // binary 0b0
+    uint5_t k5 = 27;         // binary 0b11011
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+    ASSERT_EQ(v5, k5);
+}
+
+TEST(UnpackAdvanced, UnalignedBitUnpacking)
+{
+    // unaligned multi-byte values will be unpacked the same as
+    // other bits, effectively reading from a large value, low-order
+    // bits first, then consuming the stream LSByte first
+    // v1 will use k[0][1:0]
+    // v2[5:0] will use k[0][7:2], v2[7:6] will use k[1][1:0]
+    // v3 will use k[1][2]
+    // v4[4:0] will use k[1][7:3] v4[12:5] will use k[2][7:0]
+    // v4[15:13] will use k[3][2:0]
+    // v5 will use k[3][3]
+    // v6[3:0] will use k[3][7:0] v6[11:4] will use k[4][7:0]
+    // v6[19:12] will use k[5][7:0] v6[27:20] will use k[6][7:0]
+    // v6[31:28] will use k[7][3:0]
+    // v7 will use k[7][7:4]
+    std::vector<uint8_t> i = {0x96, 0xd2, 0x2a, 0xcd, 0xd3, 0x3b, 0xbc, 0x9d};
+    ipmi::message::Payload p(std::forward<std::vector<uint8_t>>(i));
+    uint2_t v1;
+    uint8_t v2;
+    bool v3;
+    uint16_t v4;
+    bool v5;
+    uint32_t v6;
+    uint4_t v7;
+    // check that the number of bytes matches
+    ASSERT_EQ(p.unpack(v1, v2, v3, v4, v5, v6, v7), 0);
+    // check that the payload was fully unpacked
+    ASSERT_TRUE(p.fullyUnpacked());
+    uint2_t k1 = 2;           // binary 0b10
+    uint8_t k2 = 0xa5;        // binary 0b10100101
+    bool k3 = false;          // binary 0b0
+    uint16_t k4 = 0xa55a;     // binary 0b1010010101011010
+    bool k5 = true;           // binary 0b1
+    uint32_t k6 = 0xdbc3bd3c; // binary 0b11011011110000111011110100111100
+    uint4_t k7 = 9;           // binary 0b1001
+    // check that the bytes were correctly unpacked (LSB first)
+    ASSERT_EQ(v1, k1);
+    ASSERT_EQ(v2, k2);
+    ASSERT_EQ(v3, k3);
+    ASSERT_EQ(v4, k4);
+    ASSERT_EQ(v5, k5);
+    ASSERT_EQ(v6, k6);
+    ASSERT_EQ(v7, k7);
+}