Add ConditionTrait.evaluate()

Sources/Testing/Traits/ConditionTrait.swift

@@ -26,7 +26,6 @@ public struct ConditionTrait: TestTrait, SuiteTrait {
     ///
     /// - Parameters:
     ///   - body: The function to call. The result of this function determines
-    ///     if the condition is satisfied or not.
     case conditional(_ body: @Sendable () async throws -> Bool)
 
     /// The trait is unconditional and always has the same result.
@@ -62,16 +61,27 @@ public struct ConditionTrait: TestTrait, SuiteTrait {
 
   /// The source location where this trait is specified.
   public var sourceLocation: SourceLocation
-
-  public func prepare(for test: Test) async throws {
-    let result = switch kind {
+
+  /// Evaluate this instance's underlying condition.
+  ///
+  /// - Returns: The result of evaluating this instance's underlying condition.
+  ///
+  /// The evaluation is performed each time this function is called, and is not
+  /// cached.
+  @_spi(Experimental)
+  public func evaluate() async throws -> Bool {
+    switch kind {
     case let .conditional(condition):
       try await condition()
     case let .unconditional(unconditionalValue):
       unconditionalValue
     }
+  }
+
+  public func prepare(for test: Test) async throws {
+    let isEnabled = try await evaluate()
 
-    if !result {
+    if !isEnabled {
       // We don't need to consider including a backtrace here because it will
       // primarily contain frames in the testing library, not user code. If an
       // error was thrown by a condition evaluated above, the caller _should_

Tests/TestingTests/RunnerTests.swift

@@ -332,6 +332,23 @@ final class RunnerTests: XCTestCase {
     let test2 = Test(.disabled(if: Bool.random())) { }
     XCTAssertTrue(test2.traits.compactMap { $0 as? ConditionTrait }.allSatisfy { !$0.isConstant })
   }
+
+  func testEvaluateConditionTrait() async throws {
+    let trueUnconditional = ConditionTrait(kind: .unconditional(true), comments: [], sourceLocation: #_sourceLocation)
+    let falseUnconditional = ConditionTrait.disabled()
+    let enabledTrue = ConditionTrait.enabled(if: true)
+    let enabledFalse = ConditionTrait.enabled(if: false)
+    var result: Bool
+
+    result = try await trueUnconditional.evaluate()
+    XCTAssertTrue(result)
+    result = try await falseUnconditional.evaluate()
+    XCTAssertFalse(result)
+    result = try await enabledTrue.evaluate()
+    XCTAssertTrue(result)
+    result = try await enabledFalse.evaluate()
+    XCTAssertFalse(result)
+  }
 
   func testGeneratedPlan() async throws {
     let tests: [(Any.Type, String)] = [