Continued swift testing adoption

Sources/TestSupport/Utilities.swift

@@ -170,7 +170,7 @@ func expectNoChanges<T: BinaryInteger>(_ check: @autoclosure () -> T, by differe
 ///
 /// - Note: `oracle` is also checked for conformance to the
 ///   laws.
-public func checkEquatable<Instances: Collection>(
+public func XCTCheckEquatable<Instances: Collection>(
     _ instances: Instances,
     oracle: (Instances.Index, Instances.Index) -> Bool,
     allowBrokenTransitivity: Bool = false,
@@ -179,7 +179,7 @@ public func checkEquatable<Instances: Collection>(
     line: UInt = #line
 ) where Instances.Element: Equatable {
     let indices = Array(instances.indices)
-    _checkEquatableImpl(
+    _XCTCheckEquatableImpl(
         Array(instances),
         oracle: { oracle(indices[$0], indices[$1]) },
         allowBrokenTransitivity: allowBrokenTransitivity,
@@ -188,15 +188,7 @@ public func checkEquatable<Instances: Collection>(
         line: line)
 }
 
-private class Box<T> {
-    var value: T
-
-    init(_ value: T) {
-        self.value = value
-    }
-}
-
-internal func _checkEquatableImpl<Instance : Equatable>(
+internal func _XCTCheckEquatableImpl<Instance : Equatable>(
     _ instances: [Instance],
     oracle: (Int, Int) -> Bool,
     allowBrokenTransitivity: Bool = false,
@@ -271,23 +263,14 @@ internal func _checkEquatableImpl<Instance : Equatable>(
     }
 }
 
-func hash<H: Hashable>(_ value: H, salt: Int? = nil) -> Int {
-    var hasher = Hasher()
-    if let salt = salt {
-        hasher.combine(salt)
-    }
-    hasher.combine(value)
-    return hasher.finalize()
-}
-
-public func checkHashable<Instances: Collection>(
+public func XCTCheckHashable<Instances: Collection>(
     _ instances: Instances,
     equalityOracle: (Instances.Index, Instances.Index) -> Bool,
     allowIncompleteHashing: Bool = false,
     _ message: @autoclosure () -> String = "",
     file: StaticString = #filePath, line: UInt = #line
 ) where Instances.Element: Hashable {
-    checkHashable(
+    XCTCheckHashable(
         instances,
         equalityOracle: equalityOracle,
         hashEqualityOracle: equalityOracle,
@@ -298,7 +281,7 @@ public func checkHashable<Instances: Collection>(
 }
 
 
-public func checkHashable<Instances: Collection>(
+public func XCTCheckHashable<Instances: Collection>(
     _ instances: Instances,
     equalityOracle: (Instances.Index, Instances.Index) -> Bool,
     hashEqualityOracle: (Instances.Index, Instances.Index) -> Bool,
@@ -307,7 +290,7 @@ public func checkHashable<Instances: Collection>(
     file: StaticString = #filePath, line: UInt = #line
 ) where Instances.Element: Hashable {
 
-    checkEquatable(
+    XCTCheckEquatable(
         instances,
         oracle: equalityOracle,
         message(),
@@ -390,7 +373,7 @@ public func checkHashable<Instances: Collection>(
 /// Test that the elements of `groups` consist of instances that satisfy the
 /// semantic requirements of `Hashable`, with each group defining a distinct
 /// equivalence class under `==`.
-public func checkHashableGroups<Groups: Collection>(
+public func XCTCheckHashableGroups<Groups: Collection>(
     _ groups: Groups,
     _ message: @autoclosure () -> String = "",
     allowIncompleteHashing: Bool = false,
@@ -405,7 +388,7 @@ public func checkHashableGroups<Groups: Collection>(
     func equalityOracle(_ lhs: Int, _ rhs: Int) -> Bool {
         return groupIndices[lhs] == groupIndices[rhs]
     }
-    checkHashable(
+    XCTCheckHashable(
         instances,
         equalityOracle: equalityOracle,
         hashEqualityOracle: equalityOracle,
@@ -477,3 +460,259 @@ func testExpectedToFailWithCheck<T>(check: (String) -> Bool, _ test:  @escaping
     }
 }
 
+// MARK: - swift-testing Helpers
+
+import Testing
+
+/// Test that the elements of `instances` satisfy the semantic
+/// requirements of `Equatable`, using `oracle` to generate equality
+/// expectations from pairs of positions in `instances`.
+///
+/// - Note: `oracle` is also checked for conformance to the
+///   laws.
+func checkEquatable<Instances : Collection>(
+    _ instances: Instances,
+    oracle: (Instances.Index, Instances.Index) -> Bool,
+    allowBrokenTransitivity: Bool = false,
+    _ message: @autoclosure () -> String = "",
+    sourceLocation: SourceLocation = #_sourceLocation
+) where Instances.Element: Equatable {
+    let indices = Array(instances.indices)
+    _checkEquatable(
+        instances,
+        oracle: { oracle(indices[$0], indices[$1]) },
+        allowBrokenTransitivity: allowBrokenTransitivity,
+        message(),
+        sourceLocation: sourceLocation
+    )
+}
+
+func _checkEquatable<Instances : Collection>(
+    _ _instances: Instances,
+    oracle: (Int, Int) -> Bool,
+    allowBrokenTransitivity: Bool = false,
+    _ message: @autoclosure () -> String = "",
+    sourceLocation: SourceLocation = #_sourceLocation
+) where Instances.Element: Equatable {
+    let instances = Array(_instances)
+
+    // For each index (which corresponds to an instance being tested) track the
+    // set of equal instances.
+    var transitivityScoreboard: [Box<Set<Int>>] =
+    instances.indices.map { _ in Box([]) }
+
+    for i in instances.indices {
+        let x = instances[i]
+        #expect(oracle(i, i), "bad oracle: broken reflexivity at index \(i)")
+
+        for j in instances.indices {
+            let y = instances[j]
+
+            let predictedXY = oracle(i, j)
+            #expect(
+                predictedXY == oracle(j, i),
+                "bad oracle: broken symmetry between indices \(i), \(j)",
+                sourceLocation: sourceLocation
+            )
+
+            let isEqualXY = x == y
+            #expect(
+                predictedXY == isEqualXY,
+                """
+                \((predictedXY
+                ? "expected equal, found not equal"
+                : "expected not equal, found equal"))
+                lhs (at index \(i)): \(String(reflecting: x))
+                rhs (at index \(j)): \(String(reflecting: y))
+                """,
+                sourceLocation: sourceLocation
+            )
+
+            // Not-equal is an inverse of equal.
+            #expect(
+                isEqualXY != (x != y),
+                """
+                lhs (at index \(i)): \(String(reflecting: x))
+                rhs (at index \(j)): \(String(reflecting: y))
+                """,
+                sourceLocation: sourceLocation
+            )
+
+            if !allowBrokenTransitivity {
+                // Check transitivity of the predicate represented by the oracle.
+                // If we are adding the instance `j` into an equivalence set, check that
+                // it is equal to every other instance in the set.
+                if predictedXY && i < j && transitivityScoreboard[i].value.insert(j).inserted {
+                    if transitivityScoreboard[i].value.count == 1 {
+                        transitivityScoreboard[i].value.insert(i)
+                    }
+                    for k in transitivityScoreboard[i].value {
+                        #expect(
+                            oracle(j, k),
+                            "bad oracle: broken transitivity at indices \(i), \(j), \(k)",
+                            sourceLocation: sourceLocation
+                        )
+                        // No need to check equality between actual values, we will check
+                        // them with the checks above.
+                    }
+                    precondition(transitivityScoreboard[j].value.isEmpty)
+                    transitivityScoreboard[j] = transitivityScoreboard[i]
+                }
+            }
+        }
+    }
+}
+
+public func checkHashable<Instances: Collection>(
+    _ instances: Instances,
+    equalityOracle: (Instances.Index, Instances.Index) -> Bool,
+    allowIncompleteHashing: Bool = false,
+    _ message: @autoclosure () -> String = "",
+    sourceLocation: SourceLocation = #_sourceLocation
+) where Instances.Element: Hashable {
+    checkHashable(
+        instances,
+        equalityOracle: equalityOracle,
+        hashEqualityOracle: equalityOracle,
+        allowIncompleteHashing: allowIncompleteHashing,
+        message(),
+        sourceLocation: sourceLocation)
+}
+
+func checkHashable<Instances: Collection>(
+    _ instances: Instances,
+    equalityOracle: (Instances.Index, Instances.Index) -> Bool,
+    hashEqualityOracle: (Instances.Index, Instances.Index) -> Bool,
+    allowIncompleteHashing: Bool = false,
+    _ message: @autoclosure () -> String = "",
+    sourceLocation: SourceLocation = #_sourceLocation
+) where Instances.Element: Hashable {
+    checkEquatable(
+        instances,
+        oracle: equalityOracle,
+        message(),
+        sourceLocation: sourceLocation
+    )
+
+    for i in instances.indices {
+        let x = instances[i]
+        for j in instances.indices {
+            let y = instances[j]
+            let predicted = hashEqualityOracle(i, j)
+            #expect(
+                predicted == hashEqualityOracle(j, i),
+                "bad hash oracle: broken symmetry between indices \(i), \(j)",
+                sourceLocation: sourceLocation
+            )
+            if x == y {
+                #expect(
+                    predicted,
+                    """
+                    bad hash oracle: equality must imply hash equality
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+            }
+            if predicted {
+                #expect(
+                    hash(x) == hash(y),
+                    """
+                    hash(into:) expected to match, found to differ
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+                #expect(
+                    x.hashValue == y.hashValue,
+                    """
+                    hashValue expected to match, found to differ
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+                #expect(
+                    x._rawHashValue(seed: 0) == y._rawHashValue(seed: 0),
+                    """
+                    _rawHashValue(seed:) expected to match, found to differ
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+            } else if !allowIncompleteHashing {
+                // Try a few different seeds; at least one of them should discriminate
+                // between the hashes. It is extremely unlikely this check will fail
+                // all ten attempts, unless the type's hash encoding is not unique,
+                // or unless the hash equality oracle is wrong.
+                #expect(
+                    (0..<10).contains { hash(x, salt: $0) != hash(y, salt: $0) },
+                    """
+                    hash(into:) expected to differ, found to match
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+                #expect(
+                    (0..<10).contains { i in
+                        x._rawHashValue(seed: i) != y._rawHashValue(seed: i)
+                    },
+                    """
+                    _rawHashValue(seed:) expected to differ, found to match
+                    lhs (at index \(i)): \(x)
+                    rhs (at index \(j)): \(y)
+                    """,
+                    sourceLocation: sourceLocation
+                )
+            }
+        }
+    }
+}
+
+/// Test that the elements of `groups` consist of instances that satisfy the
+/// semantic requirements of `Hashable`, with each group defining a distinct
+/// equivalence class under `==`.
+public func checkHashableGroups<Groups: Collection>(
+    _ groups: Groups,
+    _ message: @autoclosure () -> String = "",
+    allowIncompleteHashing: Bool = false,
+    sourceLocation: SourceLocation = #_sourceLocation
+) where Groups.Element: Collection, Groups.Element.Element: Hashable {
+    let instances = groups.flatMap { $0 }
+    // groupIndices[i] is the index of the element in groups that contains
+    // instances[i].
+    let groupIndices =
+    zip(0..., groups).flatMap { i, group in group.map { _ in i } }
+    func equalityOracle(_ lhs: Int, _ rhs: Int) -> Bool {
+        return groupIndices[lhs] == groupIndices[rhs]
+    }
+    checkHashable(
+        instances,
+        equalityOracle: equalityOracle,
+        hashEqualityOracle: equalityOracle,
+        allowIncompleteHashing: allowIncompleteHashing,
+        sourceLocation: sourceLocation)
+}
+
+// MARK: - Private Types
+
+private class Box<T> {
+    var value: T
+
+    init(_ value: T) {
+        self.value = value
+    }
+}
+
+private func hash<H: Hashable>(_ value: H, salt: Int? = nil) -> Int {
+    var hasher = Hasher()
+    if let salt = salt {
+        hasher.combine(salt)
+    }
+    hasher.combine(value)
+    return hasher.finalize()
+}