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+# Unit Test Framework Package
+
+## About
+
+This package adds a unit test framework capable of building tests for multiple contexts including
+the UEFI shell environment and host-based environments. It allows for unit test development to focus
+on the tests and leave error logging, result formatting, context persistance, and test running to the framework.
+The unit test framework works well for low level unit tests as well as system level tests and
+fits easily in automation frameworks.
+
+### UnitTestLib
+
+The main "framework" library. The core of the framework is the Framework object, which can have any number
+of test cases and test suites registered with it. The Framework object is also what drives test execution.
+
+The Framework also provides helper macros and functions for checking test conditions and
+reporting errors. Status and error info will be logged into the test context. There are a number
+of Assert macros that make the unit test code friendly to view and easy to understand.
+
+Finally, the Framework also supports logging strings during the test execution. This data is logged
+to the test context and will be available in the test reporting phase. This should be used for
+logging test details and helpful messages to resolve test failures.
+
+### UnitTestPersistenceLib
+
+Persistence lib has the main job of saving and restoring test context to a storage medium so that for tests
+that require exiting the active process and then resuming state can be maintained. This is critical
+in supporting a system reboot in the middle of a test run.
+
+### UnitTestResultReportLib
+
+Library provides function to run at the end of a framework test run and handles formatting the report.
+This is a common customization point and allows the unit test framework to fit its output reports into
+other test infrastructure. In this package a simple library instances has been supplied to output test
+results to the console as plain text.
+
+## Samples
+
+There is a sample unit test provided as both an example of how to write a unit test and leverage
+many of the features of the framework. This sample can be found in the `Test/UnitTest/Sample/SampleUnitTest`
+directory.
+
+The sample is provided in PEI, SMM, DXE, and UEFI App flavors. It also has a flavor for the HOST_APPLICATION
+build type, which can be run on a host system without needing a target.
+
+## Usage
+
+This section is built a lot like a "Getting Started". We'll go through some of the components that are needed
+when constructing a unit test and some of the decisions that are made by the test writer. We'll also describe
+how to check for expected conditions in test cases and a bit of the logging characteristics.
+
+Most of these examples will refer to the SampleUnitTestUefiShell app found in this package.
+
+### Requirements - INF
+
+In our INF file, we'll need to bring in the `UnitTestLib` library. Conveniently, the interface
+header for the `UnitTestLib` is located in `MdePkg`, so you shouldn't need to depend on any other
+packages. As long as your DSC file knows where to find the lib implementation that you want to use,
+you should be good to go.
+
+See this example in 'SampleUnitTestApp.inf'...
+
+```
+[Packages]
+  MdePkg/MdePkg.dec
+
+[LibraryClasses]
+  UefiApplicationEntryPoint
+  BaseLib
+  DebugLib
+  UnitTestLib
+  PrintLib
+```
+
+### Requirements - Code
+
+Not to state the obvious, but let's make sure we have the following include before getting too far along...
+
+```c
+#include <Library/UnitTestLib.h>
+```
+
+Now that we've got that squared away, let's look at our 'Main()'' routine (or DriverEntryPoint() or whatever).
+
+### Configuring the Framework
+
+Everything in the UnitTestPkg framework is built around an object called -- conveniently -- the Framework.
+This Framework object will contain all the information about our test, the test suites and test cases associated
+with it, the current location within the test pass, and any results that have been recorded so far.
+
+To get started with a test, we must first create a Framework instance. The function for this is
+`InitUnitTestFramework`. It takes in `CHAR8` strings for the long name, short name, and test version.
+The long name and version strings are just for user presentation and relatively flexible. The short name
+will be used to name any cache files and/or test results, so should be a name that makes sense in that context.
+These strings are copied internally to the Framework, so using stack-allocated or literal strings is fine.
+
+In the 'SampleUnitTestUefiShell' app, the module name is used as the short name, so the init looks like this.
+
+```c
+DEBUG(( DEBUG_INFO, "%a v%a\n", UNIT_TEST_APP_NAME, UNIT_TEST_APP_VERSION ));
+
+//
+// Start setting up the test framework for running the tests.
+//
+Status = InitUnitTestFramework( &Framework, UNIT_TEST_APP_NAME, gEfiCallerBaseName, UNIT_TEST_APP_VERSION );
+```
+
+The `&Framework` returned here is the handle to the Framework. If it's successfully returned, we can start adding
+test suites and test cases.
+
+Test suites exist purely to help organize test cases and to differentiate the results in reports. If you're writing
+a small unit test, you can conceivably put all test cases into a single suite. However, if you end up with 20+ test
+cases, it may be beneficial to organize them according to purpose. You _must_ have at least one test suite, even if
+it's just a catch-all. The function to create a test suite is `CreateUnitTestSuite`. It takes in a handle to
+the Framework object, a `CHAR8` string for the suite title and package name, and optional function pointers for
+a setup function and a teardown function.
+
+The suite title is for user presentation. The package name is for xUnit type reporting and uses a '.'-separated
+hierarchical format (see 'SampleUnitTestApp' for example). If provided, the setup and teardown functions will be
+called once at the start of the suite (before _any_ tests have run) and once at the end of the suite (after _all_
+tests have run), respectively. If either or both of these are unneeded, pass `NULL`. The function prototypes are
+`UNIT_TEST_SUITE_SETUP` and `UNIT_TEST_SUITE_TEARDOWN`.
+
+Looking at 'SampleUnitTestUefiShell' app, you can see that the first test suite is created as below...
+
+```c
+//
+// Populate the SimpleMathTests Unit Test Suite.
+//
+Status = CreateUnitTestSuite( &SimpleMathTests, Fw, "Simple Math Tests", "Sample.Math", NULL, NULL );
+```
+
+This test suite has no setup or teardown functions. The `&SimpleMathTests` returned here is a handle to the suite and
+will be used when adding test cases.
+
+Great! Now we've finished some of the cruft, red tape, and busy work. We're ready to add some tests. Adding a test
+to a test suite is accomplished with the -- you guessed it -- `AddTestCase` function. It takes in the suite handle;
+a `CHAR8` string for the description and class name; a function pointer for the test case itself; additional, optional
+function pointers for prerequisite check and cleanup routines; and and optional pointer to a context structure.
+
+Okay, that's a lot. Let's take it one piece at a time. The description and class name strings are very similar in
+usage to the suite title and package name strings in the test suites. The former is for user presentation and the
+latter is for xUnit parsing. The test case function pointer is what is actually executed as the "test" and the
+prototype should be `UNIT_TEST_FUNCTION`. The last three parameters require a little bit more explaining.
+
+The prerequisite check function has a prototype of `UNIT_TEST_PREREQUISITE` and -- if provided -- will be called
+immediately before the test case. If this function returns any error, the test case will not be run and will be
+recorded as `UNIT_TEST_ERROR_PREREQUISITE_NOT_MET`. The cleanup function (prototype `UNIT_TEST_CLEANUP`) will be called
+immediately after the test case to provide an opportunity to reset any global state that may have been changed in the
+test case. In the event of a prerequisite failure, the cleanup function will also be skipped. If either of these
+functions is not needed, pass `NULL`.
+
+The context pointer is entirely case-specific. It will be passed to the test case upon execution. One of the purposes
+of the context pointer is to allow test case reuse with different input data. (Another use is for testing that wraps
+around a system reboot, but that's beyond the scope of this guide.) The test case must know how to interpret the context
+pointer, so it could be a simple value, or it could be a complex structure. If unneeded, pass `NULL`.
+
+In 'SampleUnitTestUefiShell' app, the first test case is added using the code below...
+
+```c
+AddTestCase( SimpleMathTests, "Adding 1 to 1 should produce 2", "Addition", OnePlusOneShouldEqualTwo, NULL, NULL, NULL );
+```
+
+This test case calls the function `OnePlusOneShouldEqualTwo` and has no prerequisite, cleanup, or context.
+
+Once all the suites and cases are added, it's time to run the Framework.
+
+```c
+//
+// Execute the tests.
+//
+Status = RunAllTestSuites( Framework );
+```
+
+### A Simple Test Case
+
+We'll take a look at the below test case from 'SampleUnitTestApp'...
+
+```c
+UNIT_TEST_STATUS
+EFIAPI
+OnePlusOneShouldEqualTwo (
+  IN UNIT_TEST_FRAMEWORK_HANDLE  Framework,
+  IN UNIT_TEST_CONTEXT           Context
+  )
+{
+  UINTN     A, B, C;
+
+  A = 1;
+  B = 1;
+  C = A + B;
+
+  UT_ASSERT_EQUAL(C, 2);
+  return UNIT_TEST_PASSED;
+} // OnePlusOneShouldEqualTwo()
+```
+
+The prototype for this function matches the `UNIT_TEST_FUNCTION` prototype. It takes in a handle to the Framework
+itself and the context pointer. The context pointer could be cast and interpreted as anything within this test case,
+which is why it's important to configure contexts carefully. The test case returns a value of `UNIT_TEST_STATUS`, which
+will be recorded in the Framework and reported at the end of all suites.
+
+In this test case, the `UT_ASSERT_EQUAL` assertion is being used to establish that the business logic has functioned
+correctly. There are several assertion macros, and you are encouraged to use one that matches as closely to your
+intended test criterium as possible, because the logging is specific to the macro and more specific macros have more
+detailed logs. When in doubt, there are always `UT_ASSERT_TRUE` and `UT_ASSERT_FALSE`. Assertion macros that fail their
+test criterium will immediately return from the test case with `UNIT_TEST_ERROR_TEST_FAILED` and log an error string.
+_Note_ that this early return can have implications for memory leakage.
+
+At the end, if all test criteria pass, you should return `UNIT_TEST_PASSED`.
+
+### More Complex Cases
+
+To write more advanced tests, first take a look at all the Assertion and Logging macros provided in the framework.
+
+Beyond that, if you're writing host-based tests and want to take a dependency on the UnitTestFrameworkPkg, you can
+leverage the `cmocka.h` interface and write tests with all the features of the Cmocka framework.
+
+Documentation for Cmocka can be found here:
+https://api.cmocka.org/
+
+## Development
+
+When using the EDK2 Pytools for CI testing, the host-based unit tests will be built and run on any build that includes the `NOOPT` build target.
+
+If you are trying to iterate on a single test, a convenient pattern is to build only that test module. For example, the following command will build only the SafeIntLib host-based test from the MdePkg...
+
+```bash
+stuart_ci_build -c .pytool/CISettings.py TOOL_CHAIN_TAG=VS2017 -p MdePkg -t NOOPT BUILDMODULE=MdePkg/Test/UnitTest/Library/BaseSafeIntLib/TestBaseSafeIntLib.inf
+```
+
+## Known Limitations
+
+### PEI, DXE, SMM
+
+While sample tests have been provided for these execution environments, only cursory build validation
+has been performed. Care has been taken while designing the frameworks to allow for execution during
+boot phases, but only UEFI Shell and host-based tests have been thoroughly evaluated. Full support for
+PEI, DXE, and SMM is forthcoming, but should be considered beta/staging for now.
+
+### Host-Based Support vs Other Tests
+
+The host-based test framework is powered internally by the Cmocka framework. As such, it has abilities
+that the target-based tests don't (yet). It would be awesome if this meant that it was a super set of
+the target-based tests, and it worked just like the target-based tests but with more features. Unfortunately,
+this is not the case. While care has been taken to keep them as close a possible, there are a few known
+inconsistencies that we're still ironing out. For example, the logging messages in the target-based tests
+are cached internally and associated with the running test case. They can be saved later as part of the
+reporting lib. This isn't currently possible with host-based. Only the assertion failures are logged.
+
+We will continue trying to make these as similar as possible.
+
+## Copyright
+
+Copyright (c) Microsoft Corporation.
+SPDX-License-Identifier: BSD-2-Clause-Patent
+