asyncChainSequence: harmonize unit tests nomenclature (#191)

Author: twittemb

Tests/AsyncAlgorithmsTests/TestChain.swift

@@ -13,57 +13,68 @@
 import AsyncAlgorithms
 
 final class TestChain2: XCTestCase {
-  func test_chain() async {
-    let chained = chain([1, 2, 3].async, [4, 5, 6].async)
+  func test_chain2_concatenates_elements_from_sequences_and_returns_nil_when_source_is_pastEnd() async {
+    let expected1 = [1, 2, 3]
+    let expected2 = [4, 5, 6]
+    let expected = expected1 + expected2
+    let chained = chain(expected1.async, expected2.async)
+
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+    var collected = [Int]()
     while let item = await iterator.next() {
-      actual.append(item)
+      collected.append(item)
     }
-    XCTAssertEqual([1, 2, 3, 4, 5, 6], actual)
+    XCTAssertEqual(expected, collected)
+
     let pastEnd = await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_throwing_first() async throws {
+  func test_chain2_outputs_elements_from_first_sequence_and_throws_when_first_throws() async throws {
     let chained = chain([1, 2, 3].async.map { try throwOn(3, $0) }, [4, 5, 6].async)
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     do {
       while let item = try await iterator.next() {
-        actual.append(item)
+        collected.append(item)
       }
-      XCTFail()
+      XCTFail("Chained sequence should throw when first sequence throws")
     } catch {
       XCTAssertEqual(Failure(), error as? Failure)
     }
-    XCTAssertEqual([1, 2], actual)
+    XCTAssertEqual([1, 2], collected)
+
     let pastEnd = try await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_throwing_second() async throws {
+  func test_chain2_outputs_elements_from_sequences_and_throws_when_second_throws() async throws {
     let chained = chain([1, 2, 3].async, [4, 5, 6].async.map { try throwOn(5, $0) })
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     do {
       while let item = try await iterator.next() {
-        actual.append(item)
+        collected.append(item)
       }
-      XCTFail()
+      XCTFail("Chained sequence should throw when second sequence throws")
     } catch {
       XCTAssertEqual(Failure(), error as? Failure)
     }
-    XCTAssertEqual([1, 2, 3, 4], actual)
+    XCTAssertEqual(collected, [1, 2, 3, 4])
+
     let pastEnd = try await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_cancellation() async {
-    let source = Indefinite(value: "test")
-    let sequence = chain(source.async, ["past indefinite"].async)
+  func test_chain2_finishes_when_task_is_cancelled() async {
     let finished = expectation(description: "finished")
     let iterated = expectation(description: "iterated")
+
+    let source = Indefinite(value: "test")
+    let sequence = chain(source.async, ["past indefinite"].async)
+
     let task = Task {
       var firstIteration = false
       for await _ in sequence {
@@ -74,84 +85,101 @@ final class TestChain2: XCTestCase {
       }
       finished.fulfill()
     }
+
     // ensure the other task actually starts
     wait(for: [iterated], timeout: 1.0)
+
     // cancellation should ensure the loop finishes
     // without regards to the remaining underlying sequence
     task.cancel()
+
     wait(for: [finished], timeout: 1.0)
   }
 }
 
 final class TestChain3: XCTestCase {
-  func test_chain() async {
-    let chained = chain([1, 2, 3].async, [4, 5, 6].async, [7, 8, 9].async)
+  func test_chain3_concatenates_elements_from_sequences_and_returns_nil_when_source_is_pastEnd() async {
+    let expected1 = [1, 2, 3]
+    let expected2 = [4, 5, 6]
+    let expected3 = [7, 8, 9]
+    let expected = expected1 + expected2 + expected3
+    let chained = chain(expected1.async, expected2.async, expected3.async)
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     while let item = await iterator.next() {
-      actual.append(item)
+      collected.append(item)
     }
-    XCTAssertEqual([1, 2, 3, 4, 5, 6, 7, 8, 9], actual)
+    XCTAssertEqual(expected, collected)
+
     let pastEnd = await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_throwing_first() async throws {
+  func test_chain3_outputs_elements_from_first_sequence_and_throws_when_first_throws() async throws {
     let chained = chain([1, 2, 3].async.map { try throwOn(3, $0) }, [4, 5, 6].async, [7, 8, 9].async)
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     do {
       while let item = try await iterator.next() {
-        actual.append(item)
+        collected.append(item)
       }
-      XCTFail()
+      XCTFail("Chained sequence should throw when first sequence throws")
     } catch {
       XCTAssertEqual(Failure(), error as? Failure)
     }
-    XCTAssertEqual([1, 2], actual)
+    XCTAssertEqual(collected, [1, 2])
+
     let pastEnd = try await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_throwing_second() async throws {
+  func test_chain3_outputs_elements_from_sequences_and_throws_when_second_throws() async throws {
     let chained = chain([1, 2, 3].async, [4, 5, 6].async.map { try throwOn(5, $0) }, [7, 8, 9].async)
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     do {
       while let item = try await iterator.next() {
-        actual.append(item)
+        collected.append(item)
       }
-      XCTFail()
+      XCTFail("Chained sequence should throw when second sequence throws")
     } catch {
       XCTAssertEqual(Failure(), error as? Failure)
     }
-    XCTAssertEqual([1, 2, 3, 4], actual)
+    XCTAssertEqual(collected, [1, 2, 3, 4])
+
     let pastEnd = try await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_throwing_third() async throws {
+  func test_chain3_outputs_elements_from_sequences_and_throws_when_third_throws() async throws {
     let chained = chain([1, 2, 3].async, [4, 5, 6].async, [7, 8, 9].async.map { try throwOn(8, $0) })
     var iterator = chained.makeAsyncIterator()
-    var actual = [Int]()
+
+    var collected = [Int]()
     do {
       while let item = try await iterator.next() {
-        actual.append(item)
+        collected.append(item)
       }
-      XCTFail()
+      XCTFail("Chained sequence should throw when third sequence throws")
     } catch {
       XCTAssertEqual(Failure(), error as? Failure)
     }
-    XCTAssertEqual([1, 2, 3, 4, 5, 6, 7], actual)
+    XCTAssertEqual(collected, [1, 2, 3, 4, 5, 6, 7])
+
     let pastEnd = try await iterator.next()
     XCTAssertNil(pastEnd)
   }
 
-  func test_cancellation() async {
-    let source = Indefinite(value: "test")
-    let sequence = chain(source.async, ["past indefinite"].async, ["and even further"].async)
+  func test_chain3_finishes_when_task_is_cancelled() async {
     let finished = expectation(description: "finished")
     let iterated = expectation(description: "iterated")
+
+    let source = Indefinite(value: "test")
+    let sequence = chain(source.async, ["past indefinite"].async, ["and even further"].async)
+
     let task = Task {
       var firstIteration = false
       for await _ in sequence {
@@ -162,11 +190,14 @@ final class TestChain3: XCTestCase {
       }
       finished.fulfill()
     }
+
     // ensure the other task actually starts
     wait(for: [iterated], timeout: 1.0)
+
     // cancellation should ensure the loop finishes
     // without regards to the remaining underlying sequence
     task.cancel()
+
     wait(for: [finished], timeout: 1.0)
   }
 }