Implement --test_filter support (#999)

Implement `--test_filter` support, as detailed in
#997. This can be
engaged via a `swift_test` target like so:

```
bazel test //:Tests --test_filter=TestModuleName.TestClassName/testMethodName
```

**Note:** If `--test_filter` is not passed into the test invocation, we
fallback to the original behavior (pass `All` into the xctest
invocation.

doc/rules.md

@@ -499,6 +499,12 @@ have the paths made absolute via swizzling by enabling the
 set the `BUILD_WORKSPACE_DIRECTORY` environment variable in your scheme to the
 root of your workspace (i.e. `$(SRCROOT)`).
 
+A subset of tests for a given target can be executed via the `--test_filter` parameter:
+
+```
+bazel test //:Tests --test_filter=TestModuleName.TestClassName/testMethodName
+```
+
 
 **ATTRIBUTES**
 

examples/apple/test_filter/BUILD

@@ -0,0 +1,51 @@
+load(
+    "//swift:swift.bzl",
+    "swift_library",
+    "swift_test",
+)
+
+swift_library(
+    name = "test_filter_lib",
+    testonly = True,
+    srcs = [
+        "FailTests.swift",
+        "PassFailTests.swift",
+        "PassTests.swift",
+        "TestHelper.swift",
+    ],
+    module_name = "test_filter",
+    target_compatible_with = ["@platforms//os:macos"],
+)
+
+# Verify that tests fail as expected without test filtering.
+swift_test(
+    name = "test_filter__baseline",
+    env = {
+        "EXPECT_FAILURE": "TRUE",
+    },
+    module_name = "test_filter",
+    target_compatible_with = ["@platforms//os:macos"],
+    deps = [":test_filter_lib"],
+)
+
+# Verify that test scope is filtered by TARGET.TEST_CLASS as expected.
+swift_test(
+    name = "test_filter__feature__target_class",
+    env = {
+        "TESTBRIDGE_TEST_ONLY": "test_filter.PassTests",
+    },
+    module_name = "test_filter",
+    target_compatible_with = ["@platforms//os:macos"],
+    deps = [":test_filter_lib"],
+)
+
+# Verify that test scope is filtered by TARGET.TEST_CLASS.TEST_METHOD as expected.
+swift_test(
+    name = "test_filter__feature__target_class_method",
+    env = {
+        "TESTBRIDGE_TEST_ONLY": "test_filter.PassFailTests/test_pass",
+    },
+    module_name = "test_filter",
+    target_compatible_with = ["@platforms//os:macos"],
+    deps = [":test_filter_lib"],
+)

examples/apple/test_filter/FailTests.swift

@@ -0,0 +1,8 @@
+import XCTest
+
+class FailTests: XCTestCase {
+
+    func test_fail() {
+        TestHelper.ExpectFailureIfNeeded()
+    }
+}

examples/apple/test_filter/PassFailTests.swift

@@ -0,0 +1,12 @@
+import XCTest
+
+class PassFailTests: XCTestCase {
+
+    func test_pass() {
+        TestHelper.Pass()
+    }
+
+    func test_fail() {
+        TestHelper.ExpectFailureIfNeeded()
+    }
+}

examples/apple/test_filter/PassTests.swift

@@ -0,0 +1,8 @@
+import XCTest
+
+class PassTests: XCTestCase {
+
+    func test_pass() {
+        TestHelper.Pass()
+    }
+}

examples/apple/test_filter/TestHelper.swift

@@ -0,0 +1,20 @@
+import XCTest
+
+enum TestHelper {
+
+    static func ExpectFailureIfNeeded() {
+        let options: XCTExpectedFailure.Options = .init()
+        options.isEnabled = ProcessInfo.processInfo.environment["EXPECT_FAILURE"] == "TRUE"
+        XCTExpectFailure("Expected failure", options: options) {
+            Fail()
+        }
+    }
+
+    static func Pass() {
+        XCTAssertTrue(true)
+    }
+
+    private static func Fail() {
+        XCTFail("Fail")
+    }
+}

swift/internal/swift_binary_test.bzl

@@ -532,6 +532,12 @@ have the paths made absolute via swizzling by enabling the
 `"apple.swizzle_absolute_xcttestsourcelocation"` feature. You'll also need to
 set the `BUILD_WORKSPACE_DIRECTORY` environment variable in your scheme to the
 root of your workspace (i.e. `$(SRCROOT)`).
+
+A subset of tests for a given target can be executed via the `--test_filter` parameter:
+
+```
+bazel test //:Tests --test_filter=TestModuleName.TestClassName/testMethodName
+```
 """,
     executable = True,
     fragments = ["cpp"],

tools/xctest_runner/xctest_runner.sh.template

@@ -54,8 +54,8 @@ fi
 
 exit_status=0
 xctest=$(xcrun -f xctest)
-# TODO(allevato): Support Bazel's --test_filter.
-DYLD_INSERT_LIBRARIES=$sanitizer_dyld_env LLVM_PROFILE_FILE="$profraw" $xctest -XCTest All "$bundle_path" || exit_status=$?
+test_filter=${TESTBRIDGE_TEST_ONLY:-All}
+DYLD_INSERT_LIBRARIES=$sanitizer_dyld_env LLVM_PROFILE_FILE="$profraw" $xctest -XCTest "$test_filter" "$bundle_path" || exit_status=$?
 
 if [[ "$exit_status" -ne 0 ]]; then
   exit "$exit_status"