LitTest

Dafny Integration Tests

The tests in this directory are run using the IntegrationTests project, which uses the xUnit-based LIT test runner from the XUnitExtensions package rather than the LLVM lit CLI.

Executing Tests from the Command Line

The xUnit LIT test interpreter is run through xUnit Theory parameterized tests, and therefore hooks into the general-purpose dotnet test command:

dotnet test --logger "console;verbosity=normal" Source/IntegrationTests

-logger "console;verbosity=normal" is optional, and increases the default logging verbosity so that you can see individual tests as the pass.

The file path of each test file, relative to this directory, is used as the display name of its corresponding test. This means you can use the --filter option to run a subset of tests, or even a single file:

dotnet test --logger "console;verbosity=normal" Source/IntegrationTests --filter DisplayName~comp/Hello.dfy

See here for more information about the dotnet test command and other supported options.

Writing tests

Lit tests use a very restricted form of command-line: executables and their arguments, piping, > and >> redirections (for respectively writing and appending stdout to a file) and 2> and 2>> redirections (for respectively writing and appending both stdout and stderr to a file).

To work cross-platform, use a number of macros: %verify, %resolve, %build, %run, %translate (with %trargs), %exits-with, %diff, %sed and others you can find defined in lit.site.cfg

Any new macros defined here must also be defied in Source/IntegrationTests/LitTests.cs

A typical simple test for a single source file that has verification errors is

// RUN: %exits-with 4 %verify "%s" > "%t"
// RUN: %diff "%s.expect" "%t"

There are many examples in the .dfy files under this directory.

If you need an extra dafny file without any verification on it, use the command:

// RUN: echo 'lit should ignore this file' 

Uniform backend testing

In order to maximum testing coverage across all supported backends, especially as additional backends are added in the future, the default command for any test that compiles and/or executes a valid Dafny program should be:

// RUN: %testDafnyForEachCompiler "%s"

This command will run the program with each backend and assert that the program output matches the content of <test file>.expect. See the TestDafny utility for more details.

Any test that manually compiles and/or executes a program against one or more backends will be flagged by CI, and should be fixed by either converting it to use %testDafnyForEachCompiler or adding a // NONUNIFORM: <reason> command to flag it as intentionally inconsistent, for tests of backend-specific externs for example.

Executing Tests from JetBrains Rider

You will likely find it more convenient to run tests from an IDE such as JetBrains Rider, with a proper JDK installed like JDK 8.

Assuming you have loaded the Dafny.sln solution in Rider, you can execute all the integration tests by right-clicking on the IntegrationTests package and selecting Run Unit Tests.

You will see a tree of running tests and their results, with lots of options for filtering and summarizing results. Note the search window in the top-left, which can be used to filter to tests matching a particular substring.

Once you have at least started running these tests at least once and this tree has been populated, you can right-click any individual test to execute it, or similarly any subset of selected tests. You will often want to start the test suite and then immediately cancel it just to populate the tree for this purpose.

Debugging Tests

The xUnit test runner supports executing commands such as %dafny by directly invoking the main entry point of the corresponding C# package (i.e. DafnyDriver), which makes running the debugger against a particular test much more convenient. By default this is disabled and the runner creates a separate dafny process just as LIT does, however. This is because the main CLI implementation currently has shared static state, which causes errors when invoking the CLI in the same process on multiple inputs in sequence, much less in parallel. Future changes will address this so that the in-process Main invocation can be used instead, however, which will likely improve performance.

To debug a single test, you change the value of the DAFNY_INTEGRATION_TESTS_IN_PROCESS environment variable to true (See https://www.jetbrains.com/help/rider/Reference__Options__Tools__Unit_Testing__Test_Runner.html), and then right-click the test you wish to debug and select Debug Selected Unit Tests. You will see exceptions if the test you are running makes multiple calls to commands like %dafny, so you may wish to remove the calls you are not interested in first, e.g. if you are debugging an issue with a specific compiler.

Updating test expect files

If you set the environment variable DAFNY_INTEGRATION_TESTS_UPDATE_EXPECT_FILE to true, then the diff command in tests will not do a comparison but instead overwrite the expected file with the actual contents. This can be useful when you need to update expect files.

Updating compiler-specific test expect files

To update compiler-specific error-aware output files for tests running with %forEachDafnyCompiler, do the following:

1. Set the environment variable DAFNY_INTEGRATION_TESTS_UPDATE_EXPECT_FILE to true (See the Debugging Tests section above on how to set the environment variables)
2. Set the environment variable DAFNY_INTEGRATION_TESTS_ROOT_DIR to the path to the dafny\Source\IntegrationTests folder
3. To additionally run only the foreach compiler tests, and specifically on one single compiler:

• Set the environment variable DAFNY_INTEGRATION_TESTS_MODE to only-multi-backend
• Set the environment variable DAFNY_INTEGRATION_TESTS_ONLY_COMPILERS to rs for rust for example. It's a comma-separated list of compiler IDs for which the tests should run

With 1. and 2. every time a compiler encounters errors on a file.dfy, it will emit a file.dfy.ID.error.expect next to that file so that we know what this file is not supported by the compiler. Make sure you set DAFNY_INTEGRATION_TESTS_UPDATE_EXPECT_FILE back to false when you don't need to update these files!