file_test

BUILD

A typical BUILD target will look like:

load("rules.bzl", "file_test")

file_test(
    name = "my_file_test",
    srcs = ["my_file_test.cpp"],
    tests = glob(["testdata/**"]),
    deps = [
        ":my_lib",
        "//testing/file_test:file_test_base",
        "@googletest//:gtest",
        "@llvm-project//llvm:Support",
    ],
)

Implementation

A typical implementation will look like:

#include "my_library.h"

#include "testing/file_test/file_test_base.h"

namespace Carbon::Testing {
namespace {

class MyFileTest : public FileTestBase {
 public:
  using FileTestBase::FileTestBase;

  // Called as part of individual test executions.
  auto Run(const llvm::SmallVector<llvm::StringRef>& test_args,
           const llvm::SmallVector<TestFile>& test_files,
           llvm::raw_pwrite_stream& stdout, llvm::raw_pwrite_stream& stderr)
      -> ErrorOr<RunResult> override {
    return MyFunctionality(test_args, stdout, stderr);
  }

  // Provides arguments which are used in tests that don't provide ARGS.
  auto GetDefaultArgs() -> llvm::SmallVector<std::string> override {
    return {"default_args", "%s"};
  }
};

}  // namespace

// Registers for the framework to construct the tests.
CARBON_FILE_TEST_FACTORY(MyFileTest);

}  // namespace Carbon::Testing

Filename `fail_` prefixes

When a run fails, information about what pieces failed are returned on RunResult. This affects whether a fail_ prefix on the file is required, including in combination with split-file tests (using the // --- <filename> comment marker).

The main test file and any split-files must have a fail_ prefix if and only if they have an associated error. An exception is that the main test file may omit fail_ when it contains split-files that have a fail_ prefix.

Content replacement

Some keywords can be inserted for content:

```
[[@TEST_NAME]]
```
Replaces with the test name, which is the filename with the extension and any fail_ or todo_ prefixes removed. For split files, this is based on the split filename.

The [[@ string is reserved for future replacements, but [[ is allowed in content (comment markers don’t allow [[).

Comment markers

Settings in files are provided in comments, similar to FileCheck syntax. bazel run :file_test -- --autoupdate automatically constructs compatible CHECK:STDOUT: and CHECK:STDERR: lines.

Supported comment markers are:

```
// AUTOUDPATE
// NOAUTOUPDATE
```
Controls whether the checks in the file will be autoupdated if –autoupdate is passed. Exactly one of these markers must be present. If the file uses splits, the marker must currently be before any splits.

When autoupdating, CHECKs will be inserted starting below AUTOUPDATE. When a CHECK has line information, autoupdate will try to insert the CHECK immediately next to the line it’s associated with, with stderr CHECKs preceding the line and stdout CHECKs following the line. When that happens, any subsequent CHECK lines without line information, or that refer to lines appearing earlier, will immediately follow. As an exception, if no STDOUT check line refers to any line in the test, all STDOUT check lines are placed at the end of the file instead of immediately after AUTOUPDATE.

When using split files, if the last split file is named // --- AUTOUPDATE-SPLIT, all CHECKs will be added there; no line associations occur.
```
// ARGS: <arguments>
```
Provides a space-separated list of arguments, which will be passed to RunWithFiles as test_args. These are intended for use by the command as arguments.

Supported replacements within arguments are:
- %s
  
  Replaced with the list of files. Currently only allowed as a standalone argument, not a substring.
- %t
  
  Replaced with ${TEST_TMPDIR}/temp_file.
- %{identifier}
  
  Replaces some implementation-specific identifier with a value. (Mappings provided by way of an optional MyFileTest::GetArgReplacements)
ARGS can be specified at most once. If not provided, the FileTestBase child is responsible for providing default arguments.
```
// SET-CAPTURE-CONSOLE-OUTPUT
```
By default, stderr and stdout are expected to be piped through provided streams. Adding this causes the test’s own stderr and stdout to be captured and added as well.

This should be avoided because we are partly ensuring that streams are an API, but is helpful when wrapping Clang, where stderr is used directly.

SET-CAPTURE-CONSOLE-OUTPUT can be specified at most once.
```
// SET-CHECK-SUBSET
```
By default, all lines of output must have a CHECK match. Adding this as a option sets it so that non-matching lines are ignored. All provided CHECK:STDOUT: and CHECK:STDERR: lines must still have a match in output.

SET-CHECK-SUBSET can be specified at most once.
```
// --- <filename>
```
By default, all file content is provided to the test as a single file in test_files. Using this marker allows the file to be split into multiple files which will all be passed to test_files.

Files are not created on disk; it’s expected the child will create an InMemoryFilesystem if needed.
```
// CHECK:STDOUT: <output line>
// CHECK:STDERR: <output line>
```
These provide a match for output from the command. See SET-CHECK-SUBSET for how to change from full to subset matching of output.

Output line matchers may contain [[@LINE+offset] and {{regex}} syntaxes, similar to FileCheck.
```
// TIP: <tip>
```
Tips like this are added by autoupdate, for example providing commands to run the test directly. Tips have no impact on validation; the marker informs autoupdate that it can update or remove them as needed.