Merge pull request #2231 from bnbarham/improve-test-error

Update assertions so that the mutation is more clear

Author: bnbarham

Sources/_SwiftSyntaxTestSupport/AssertEqualWithDiff.swift

@@ -88,6 +88,8 @@ public func failStringsEqualWithDiff(
  file: StaticString = #file,
  line: UInt = #line
 ) {
+ let stringComparison: String
+
  // Use `CollectionDifference` on supported platforms to get `diff`-like line-based output. On
  // older platforms, fall back to simple string comparison.
  if #available(macOS 10.15, *) {
@@ -127,19 +129,27 @@ public func failStringsEqualWithDiff(
  }
  }
 
- let failureMessage = "Actual output (+) differed from expected output (-):\n\(result)"
- var fullMessage = message.isEmpty ? failureMessage : "\(message) - \(failureMessage)"
- if let additionalInfo = additionalInfo() {
- fullMessage = """
- \(fullMessage)
- \(additionalInfo)
- """
- }
- XCTFail(fullMessage, file: file, line: line)
+ stringComparison = result
  } else {
  // Fall back to simple message on platforms that don't support CollectionDifference.
- let failureMessage = "Actual output differed from expected output:"
- let fullMessage = message.isEmpty ? failureMessage : "\(message) - \(failureMessage)"
- XCTFail(fullMessage, file: file, line: line)
+ stringComparison = """
+ Expected:
+ \(expected)
+
+ Actual:
+ \(actual)
+ """
+ }
+
+ var fullMessage = """
+ \(message.isEmpty ? "Actual output does not match the expected" : message)
+ \(stringComparison)
+ """
+ if let additional = additionalInfo() {
+ fullMessage = """
+ \(fullMessage)
+ \(additional)
+ """
  }
+ XCTFail(fullMessage, file: file, line: line)
 }

Tests/SwiftParserTest/Assertions.swift

@@ -531,7 +531,7 @@ public struct AssertParseOptions: OptionSet {
 extension ParserTestCase {
  /// After a test case has been mutated, assert that the mutated source
  /// round-trips and doesn’t hit any assertion failures in the parser.
- fileprivate func assertRoundTrip<S: SyntaxProtocol>(
+ fileprivate func assertMutationRoundTrip<S: SyntaxProtocol>(
  source: [UInt8],
  _ parse: (inout Parser) -> S,
  experimentalFeatures: Parser.ExperimentalFeatures,
@@ -549,13 +549,9 @@ extension ParserTestCase {
  assertStringsEqualWithDiff(
  "\(mutatedTree)",
  mutatedSource,
+ "A mutation of the original test case failed to round-trip",
  additionalInfo: """
- Mutated source failed to round-trip.
-
- Mutated source:
- \(mutatedSource)
-
- Actual syntax tree:
+ Parsed syntax tree of mutation:
  \(mutatedTree.debugDescription)
  """,
  file: file,
@@ -617,10 +613,9 @@ extension ParserTestCase {
  assertStringsEqualWithDiff(
  "\(tree)",
  source,
+ "Test case failed to round-trip",
  additionalInfo: """
- Source failed to round-trip.
-
- Actual syntax tree:
+ Parsed syntax tree:
  \(tree.debugDescription)
  """,
  file: file,
@@ -682,7 +677,7 @@ extension ParserTestCase {
  }
 
  if expectedDiagnostics.allSatisfy({ $0.fixIts.isEmpty }) && expectedFixedSource != nil {
- XCTFail("A fixed source was provided but the test case produces no diagnostics with Fix-Its", file: file, line: line)
+ XCTFail("Fixed source was provided but the test case produces no diagnostics with Fix-Its", file: file, line: line)
  }
 
  if expectedDiagnostics.isEmpty && diags.isEmpty {
@@ -693,7 +688,7 @@ extension ParserTestCase {
  DispatchQueue.concurrentPerform(iterations: Array(tree.tokens(viewMode: .all)).count) { tokenIndex in
  let flippedTokenTree = TokenPresenceFlipper(flipTokenAtIndex: tokenIndex).rewrite(Syntax(tree))
  _ = ParseDiagnosticsGenerator.diagnostics(for: flippedTokenTree)
- assertRoundTrip(source: flippedTokenTree.syntaxTextBytes, parse, experimentalFeatures: experimentalFeatures, file: file, line: line)
+ assertMutationRoundTrip(source: flippedTokenTree.syntaxTextBytes, parse, experimentalFeatures: experimentalFeatures, file: file, line: line)
  }
 
  #if SWIFTPARSER_ENABLE_ALTERNATE_TOKEN_INTROSPECTION
@@ -703,7 +698,7 @@ extension ParserTestCase {
  DispatchQueue.concurrentPerform(iterations: mutations.count) { index in
  let mutation = mutations[index]
  let alternateSource = MutatedTreePrinter.print(tree: Syntax(tree), mutations: [mutation.offset: mutation.replacement])
- assertRoundTrip(source: alternateSource, parse, experimentalFeatures: experimentalFeatures, file: file, line: line)
+ assertMutationRoundTrip(source: alternateSource, parse, experimentalFeatures: experimentalFeatures, file: file, line: line)
  }
  #endif
  }