diff --git a/test/str/buf.cpp b/test/str/buf.cpp
new file mode 100644
index 0000000..dc94e2c
--- /dev/null
+++ b/test/str/buf.cpp
@@ -0,0 +1,183 @@
+#include <stdplus/str/buf.hpp>
+#include <stdplus/str/cexpr.hpp>
+
+#include <gtest/gtest.h>
+
+namespace stdplus
+{
+
+static constexpr auto makeIncStr(std::size_t len)
+{
+    stdplus::StrBuf ret;
+    auto ptr = ret.append(len);
+    for (std::size_t i = 0; i < len; i++)
+    {
+        ptr[i] = 'A' + (i % 26);
+    }
+    return ret;
+}
+
+constexpr auto data = cexprSv<[]() { return makeIncStr(sizeof(StrBuf) + 10); }>;
+// constexpr auto data = cexprSv<[]() { return makeIncStr(32); }>;
+
+TEST(StrBuf, BasicInline)
+{
+    StrBuf buf;
+    EXPECT_EQ(buf.size(), 0);
+    auto old_ptr = buf.begin();
+
+    // Ensure that we inline small amounts of data only
+    std::copy(data.begin(), data.begin() + 4, buf.append(4));
+    EXPECT_EQ(buf.begin(), old_ptr);
+    EXPECT_EQ(buf.size(), 4);
+    EXPECT_EQ(std::string_view(data).substr(0, 4), buf);
+
+    // Ensure that the max data size inline doesn't dynamically allocate
+    constexpr std::size_t max_size = sizeof(StrBuf) - sizeof(std::size_t);
+    buf.append(max_size - 4);
+    EXPECT_EQ(buf.begin(), old_ptr);
+    EXPECT_EQ(buf.size(), max_size);
+}
+
+TEST(StrBuf, DynamicAppend)
+{
+    constexpr std::size_t seg = 15;
+
+    StrBuf buf;
+    auto old_ptr = buf.begin();
+    std::copy(data.begin(), data.begin() + seg, buf.append(seg));
+
+    // Ensure that inline -> dynamic is working
+    std::copy(data.begin() + seg, data.end(), buf.append(data.size() - seg));
+    EXPECT_NE(buf.begin(), old_ptr);
+    EXPECT_EQ(data, buf);
+    EXPECT_EQ(data.size(), buf.size());
+
+    // Ensure dynamic allocation is large enough to allow additional
+    // small appends with no reallocation
+    old_ptr = buf.begin();
+    std::copy(data.begin(), data.begin() + seg, buf.append(seg));
+    EXPECT_EQ(buf.begin(), old_ptr);
+    EXPECT_EQ(data.size() + seg, buf.size());
+    EXPECT_EQ(data.substr(0, seg), std::string_view{buf}.substr(data.size()));
+
+    // Ensure new dynamic allocations copy
+    std::copy(data.begin() + seg, data.end(), buf.append(data.size() - seg));
+    EXPECT_NE(buf.begin(), old_ptr);
+    EXPECT_EQ(data.size() << 1, buf.size());
+    EXPECT_EQ(data, std::string_view{buf}.substr(0, data.size()));
+    EXPECT_EQ(data, std::string_view{buf}.substr(data.size()));
+}
+
+TEST(StrBuf, CopiesInline)
+{
+    StrBuf buf1;
+    buf1.append(1)[0] = 'a';
+    StrBuf buf2 = buf1;
+    EXPECT_EQ(buf1, buf2);
+    buf1.append(1)[0] = 'b';
+    StrBuf buf3 = buf1;
+    EXPECT_EQ("ab", buf3);
+    EXPECT_EQ("ab", buf1);
+    EXPECT_EQ("a", buf2);
+    buf3 = buf2;
+    EXPECT_EQ("a", buf3);
+    EXPECT_EQ("ab", buf1);
+    EXPECT_EQ("a", buf2);
+}
+
+TEST(StrBuf, MoveInline)
+{
+    StrBuf buf1;
+    buf1.append(1)[0] = 'a';
+    StrBuf buf2 = std::move(buf1);
+    EXPECT_EQ("a", std::string_view{buf2});
+    buf2.append(1)[0] = 'b';
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
+    EXPECT_EQ(0, buf1.size());
+    StrBuf buf3 = buf1;
+    EXPECT_EQ(0, buf3.size());
+    buf3 = std::move(buf2);
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
+    EXPECT_EQ(0, buf2.size());
+    EXPECT_EQ("ab", std::string_view{buf3});
+}
+
+TEST(StrBuf, CopyInlToDyn)
+{
+    StrBuf buf1;
+    buf1.append(1)[0] = 'a';
+    StrBuf buf2;
+    buf2.append(sizeof(StrBuf) + 10);
+    buf2 = buf1;
+    EXPECT_EQ("a", buf2);
+}
+
+TEST(StrBuf, MoveInlToDyn)
+{
+    StrBuf buf1;
+    buf1.append(1)[0] = 'a';
+    StrBuf buf2;
+    buf2.append(sizeof(StrBuf) + 10);
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
+    buf2 = std::move(buf1);
+    EXPECT_EQ("", buf1);
+    EXPECT_EQ("a", buf2);
+}
+
+TEST(StrBuf, MoveDynToInl)
+{
+    StrBuf buf1;
+    std::copy(data.begin(), data.end(), buf1.append(data.size()));
+    StrBuf buf2;
+    buf2.append(1)[0] = 'a';
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
+    buf2 = std::move(buf1);
+    EXPECT_EQ("", buf1);
+    EXPECT_EQ(data, buf2);
+}
+
+TEST(StrBuf, MoveDynToDyn)
+{
+    StrBuf buf1;
+    std::copy(data.begin(), data.end(), buf1.append(data.size()));
+    StrBuf buf2;
+    buf2.append(data.size());
+    // NOLINTNEXTLINE(clang-analyzer-cplusplus.Move)
+    buf2 = std::move(buf1);
+    EXPECT_EQ("", buf1);
+    EXPECT_EQ(data, buf2);
+}
+
+TEST(StrBuf, CopyDynToInl)
+{
+    StrBuf buf1;
+    buf1.append(data.size());
+    buf1.reset();
+    buf1.append(1)[0] = 'a';
+    StrBuf buf2 = buf1;
+    StrBuf buf3;
+    buf3.append(1)[0] = 'b';
+    buf3 = buf1;
+    EXPECT_EQ("a", buf1);
+    EXPECT_EQ("a", buf2);
+    EXPECT_EQ("a", buf3);
+}
+
+TEST(StrBuf, CopyDynToDyn)
+{
+    StrBuf buf1;
+    std::copy(data.begin(), data.end(), buf1.append(data.size()));
+    std::copy(data.begin(), data.end(), buf1.append(data.size()));
+    StrBuf buf2 = buf1;
+    StrBuf buf3;
+    std::copy(data.begin(), data.end(), buf3.append(data.size()));
+    buf3 = buf1;
+    EXPECT_EQ(buf2, buf1);
+    EXPECT_EQ(buf3, buf1);
+    buf3.append(1)[0] = 'a';
+    buf1 = buf3;
+    EXPECT_EQ(buf3, buf1);
+}
+
+} // namespace stdplus