Jacoco 代码覆盖率：不存在静态块仅显示 75% 覆盖率

Question

我在 BrickSortParallel 类中有两个静态方法。它们完全被单元测试覆盖。但我列出了一个静态块

static {...}

，Jacoco 的代码覆盖率只有 75%。这意味着什么？

public static int computeOddTaskCount(int length) {
    if (length < 0) throw new IllegalArgumentException("Illegal argument value: " + length);
    return isOdd(length) ? length >> 1 : abs(length - 1) >> 1;
  }

  public static int computeEvenTaskCount(int length) {
    if (length < 0) throw new IllegalArgumentException("Illegal argument value: " + length);
    return length >> 1;
  }

以下是确保上述方法的完整代码覆盖率的测试用例：

class ComputeTaskCountTest {

private static final String ZERO_TASKS_EXPECTED = "Zero tasks expected.";
  private static final String ONE_TASK_EXPECTED = "One task expected.";
  private static final String HALF_TASKS_EXPECTED = "Half tasks expected.";
  private static final String ILLEGAL_LENGTH_EXPECTED = "Illegal length expected.";

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testZeroLength")
    void testZeroLength() {
      assertEquals(0, computeOddTaskCount(0), ZERO_TASKS_EXPECTED);
      assertEquals(0, computeEvenTaskCount(0), ZERO_TASKS_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testMinusOneLength")
    void testMinusOneLength() {
      assertThrows(
          IllegalArgumentException.class, () -> computeOddTaskCount(-1), ILLEGAL_LENGTH_EXPECTED);
      assertThrows(
          IllegalArgumentException.class, () -> computeEvenTaskCount(-1), ILLEGAL_LENGTH_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testMinusTwoLength")
    void testMinusTwoLength() {
      assertThrows(
          IllegalArgumentException.class, () -> computeOddTaskCount(-2), ILLEGAL_LENGTH_EXPECTED);
      assertThrows(
          IllegalArgumentException.class, () -> computeEvenTaskCount(-2), ILLEGAL_LENGTH_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testMinValueLength")
    void testMinValueLength() {
      assertThrows(
          IllegalArgumentException.class,
          () -> computeOddTaskCount(Integer.MIN_VALUE),
          ILLEGAL_LENGTH_EXPECTED);
      assertThrows(
          IllegalArgumentException.class,
          () -> computeEvenTaskCount(Integer.MIN_VALUE),
          ILLEGAL_LENGTH_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testOneValueLength")
    void testOneValueLength() {
      assertEquals(0, computeOddTaskCount(1), ZERO_TASKS_EXPECTED);
      assertEquals(0, computeEvenTaskCount(1), ZERO_TASKS_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testTwoValueLength")
    void testTwoValueLength() {
      assertEquals(0, computeOddTaskCount(2), ZERO_TASKS_EXPECTED);
      assertEquals(1, computeEvenTaskCount(2), ONE_TASK_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testThreeValueLength")
    void testThreeValueLength() {
      assertEquals(1, computeOddTaskCount(3), ONE_TASK_EXPECTED);
      assertEquals(1, computeEvenTaskCount(3), ONE_TASK_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testFourValueLength")
    void testFourValueLength() {
      assertEquals(1, computeOddTaskCount(4), ONE_TASK_EXPECTED);
      assertEquals(2, computeEvenTaskCount(4), "Two tasks expected");
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testMaxValueLength")
    void testMaxValueLength() {
      assertEquals(
          Integer.MAX_VALUE / 2, computeOddTaskCount(Integer.MAX_VALUE), HALF_TASKS_EXPECTED);
      assertEquals(
          Integer.MAX_VALUE / 2, computeEvenTaskCount(Integer.MAX_VALUE), HALF_TASKS_EXPECTED);
    }

    @Test
    @DisplayName("BrickSortParallelTest.ComputeTaskCountTest.testMaxValueLengthEven")
    void testMaxValueLengthEven() {
      assertEquals(
          (Integer.MAX_VALUE - 2) / 2,
          computeOddTaskCount(Integer.MAX_VALUE - 1),
          HALF_TASKS_EXPECTED);
      assertEquals(
          (Integer.MAX_VALUE - 1) / 2,
          computeEvenTaskCount(Integer.MAX_VALUE - 1),
          HALF_TASKS_EXPECTED);
    }
  }

我在上面的测试课中遗漏了什么吗？

完整课程可在以下网址获得：

https://raw.githubusercontent.com/linusjf/DSAlgos/master/src/test/java/ds/tests/BrickSortParallelTest.java

https://raw.githubusercontent.com/linusjf/DSAlgos/master/src/main/java/ds/BrickSortParallel.java

$ java --version
openjdk 11.0.8 2020-07-14
OpenJDK Runtime Environment (build 11.0.8+10)
OpenJDK 64-Bit Server VM (build 11.0.8+10, mixed mode)

Jacoco版本：0.85

从报告来看，静态块的圈复杂度为 2，并且仅覆盖一个分支，这意味着缺少一个 测试用例来覆盖这种可能性。

Answer 1

引用 Jacoco Github 上的 Marc R Hoffman ：

“您的代码使用了断言关键字，这会产生静态初始值设定项：

static {};
  descriptor: ()V
  flags: (0x0008) ACC_STATIC
  Code:
    stack=1, locals=0, args_size=0
       0: ldc           #72                 // class ds/BrickSortParallel
       2: invokevirtual #73                 // Method java/lang/Class.desiredAssertionStatus:()Z
       5: ifne          12
       8: iconst_1
       9: goto          13
      12: iconst_0
      13: putstatic     #31                 // Field $assertionsDisabled:Z
      16: return
    LineNumberTable:
      line 19: 0
    StackMapTable: number_of_entries = 2
      frame_type = 12 /* same */
      frame_type = 64 /* same_locals_1_stack_item */
        stack = [ int ]

这是一个已知的限制。解决方法是不使用断言。”

以下代码片段解决了这个难题：

  @Generated
private void assertEquality(int  size, int count) {
if (size != count)
 throw new AssertionError("Size is not the same as count.");
    }

它会抛出 AssertionError，但

@Generated

注释可以满足代码覆盖率要求。然而，这是一种解决方法。解决方案是等待 Jacoco 在字节代码中提供所需的断言过滤。

过滤断言是一项正在进行的工作。