pcie_bifurcation: Fetch bifurcation at a PCIe slot with hardcoded values

This will read a json config and return the bifurcation based on that.
It will read the configure file in a persistent file to see if it is
valid machine config and return the bifurcation information
accordingly.

For example,
If it is valid config, it will return 8x8 for PE1,3,4,6.

Tested:
Unit tests passed.

Physical Tests.

PE0 -> no bifurcation
PE1 -> x8x8

```
$ ipmitool raw 0x2e 0x32 0x79 0x2b 0x00 0x0f 0
 79 2b 00 0b 00

$ ipmitool raw 0x2e 0x32 0x79 0x2b 0x00 0x0f 1
 79 2b 00 0b 02 08 08
```

Change-Id: I44aefbfb26372f8bc0069343c8a6d07d3cf6f42d
Signed-off-by: Willy Tu <wltu@google.com>
diff --git a/test/handler_mock.hpp b/test/handler_mock.hpp
index 2fb8e2a..9961fa8 100644
--- a/test/handler_mock.hpp
+++ b/test/handler_mock.hpp
@@ -62,6 +62,7 @@
     MOCK_METHOD(void, accelOobWrite,
                 (std::string_view, uint64_t, uint8_t, uint64_t),
                 (const, override));
+    MOCK_METHOD(std::vector<uint8_t>, pcieBifurcation, (uint8_t), (override));
 };
 
 } // namespace ipmi
diff --git a/test/handler_unittest.cpp b/test/handler_unittest.cpp
index 418ba46..2edb977 100644
--- a/test/handler_unittest.cpp
+++ b/test/handler_unittest.cpp
@@ -18,7 +18,10 @@
 
 #include <systemd/sd-bus.h>
 
+#include <charconv>
+#include <filesystem>
 #include <fstream>
+#include <functional>
 #include <nlohmann/json.hpp>
 #include <sdbusplus/message.hpp>
 #include <sdbusplus/test/sdbus_mock.hpp>
@@ -32,6 +35,9 @@
 namespace ipmi
 {
 
+using testing::_;
+using testing::Return;
+
 TEST(HandlerTest, EthCheckValidHappy)
 {
     Handler h;
@@ -112,6 +118,7 @@
 
 using ::testing::_;
 using ::testing::AnyNumber;
+using ::testing::ContainerEq;
 using ::testing::DoAll;
 using ::testing::ElementsAre;
 using ::testing::Eq;
@@ -586,6 +593,50 @@
                  IpmiException);
 }
 
+TEST(HandlerTest, PcieBifurcation)
+{
+    const std::string& testJson = "/tmp/test-json";
+    auto j = R"(
+        {
+            "1": [ 1, 3 ],
+            "3": [ 3, 6 ],
+            "4": [ 3, 4, 1 ],
+            "6": [ 8 ]
+        }
+    )"_json;
+
+    std::ofstream bifurcationJson(testJson);
+    bifurcationJson << j.dump();
+    bifurcationJson.flush();
+    bifurcationJson.close();
+
+    BifurcationStatic bifurcationHelper(testJson);
+    Handler h(std::ref(bifurcationHelper));
+
+    std::unordered_map<uint8_t, std::vector<uint8_t>> expectedMapping = {
+        {1, {1, 3}}, {3, {3, 6}}, {4, {3, 4, 1}}, {6, {8}}};
+    std::vector<uint8_t> invalidBus = {0, 2, 5, 7};
+
+    for (const auto& [bus, output] : expectedMapping)
+    {
+        EXPECT_THAT(h.pcieBifurcation(bus), ContainerEq(output));
+    }
+
+    for (const auto& bus : invalidBus)
+    {
+        EXPECT_TRUE(h.pcieBifurcation(bus).empty());
+    }
+
+    std::filesystem::remove(testJson.data());
+    bifurcationHelper = BifurcationStatic(testJson);
+    Handler h2(std::ref(bifurcationHelper));
+    for (uint8_t i = 0; i < 8; ++i)
+    {
+        auto bifurcation = h2.pcieBifurcation(i);
+        EXPECT_TRUE(bifurcation.empty());
+    }
+}
+
 // TODO: Add checks for other functions of handler.
 
 } // namespace ipmi
diff --git a/test/meson.build b/test/meson.build
index 9c579bd..f2c11a2 100644
--- a/test/meson.build
+++ b/test/meson.build
@@ -27,6 +27,7 @@
   'pcie',
   'poweroff',
   'psu',
+  'pcie_bifurcation',
 ]
 
 foreach t : tests
diff --git a/test/pcie_bifurcation_unittest.cpp b/test/pcie_bifurcation_unittest.cpp
new file mode 100644
index 0000000..90e81e4
--- /dev/null
+++ b/test/pcie_bifurcation_unittest.cpp
@@ -0,0 +1,74 @@
+// Copyright 2022 Google LLC
+//
+// 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 "commands.hpp"
+#include "handler_mock.hpp"
+#include "helper.hpp"
+#include "pcie_bifurcation.hpp"
+
+#include <vector>
+
+#include <gtest/gtest.h>
+
+using ::testing::Return;
+
+namespace google
+{
+namespace ipmi
+{
+
+using testing::_;
+using ::testing::ContainerEq;
+
+TEST(PcieBifurcationCommandTest, InvalidRequest)
+{
+    std::vector<uint8_t> request = {};
+
+    HandlerMock hMock;
+    EXPECT_EQ(::ipmi::responseReqDataLenInvalid(),
+              pcieBifurcation(request, &hMock));
+}
+
+TEST(PcieBifurcationCommandTest, ValidRequest)
+{
+    std::vector<uint8_t> request = {5};
+    std::vector<uint8_t> expectedOutput = {4, 8, 1, 2};
+
+    HandlerMock hMock;
+    EXPECT_CALL(hMock, pcieBifurcation(5)).WillOnce(Return(expectedOutput));
+
+    auto reply = pcieBifurcation(request, &hMock);
+    auto result = ValidateReply(reply);
+    auto& data = result.second;
+
+    EXPECT_EQ(sizeof(struct PcieBifurcationReply) + expectedOutput.size(),
+              data.size());
+    EXPECT_EQ(SysOEMCommands::SysPCIeSlotBifurcation, result.first);
+    EXPECT_THAT(std::vector<uint8_t>(data.begin() + 1, data.end()),
+                ContainerEq(expectedOutput));
+}
+
+TEST(PcieBifurcationCommandTest, ReplyExceddedMaxValue)
+{
+    std::vector<uint8_t> request = {5};
+    std::vector<uint8_t> expectedOutput(64, 1);
+
+    HandlerMock hMock;
+    EXPECT_CALL(hMock, pcieBifurcation(5)).WillOnce(Return(expectedOutput));
+    EXPECT_EQ(::ipmi::responseInvalidCommand(),
+              pcieBifurcation(request, &hMock));
+}
+
+} // namespace ipmi
+} // namespace google