Jacoco代码覆盖率：不存在的静态块仅显示75％的覆盖率

如何解决Jacoco代码覆盖率：不存在的静态块仅显示75％的覆盖率

我在BrickSortParallel类中有两个静态方法。它们被单元测试完全覆盖。但是我列出了一个静态块static {...}，其中Jacoco仅覆盖了75％的代码。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),() -> computeEvenTaskCount(-2),ILLEGAL_LENGTH_EXPECTED);
    }

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

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

我在上述考试课程中错过了什么吗？

有关完整课程，请访问：

https://raw.githubusercontent.com/Fernal73/DSAlgos/master/src/test/java/ds/tests/BrickSortParallelTest.java

https://raw.githubusercontent.com/Fernal73/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

从报告中可以看出，静态块的圈复杂度为2，并且只覆盖了一个分支，这意味着存在test case missing to cover that eventuality。

解决方法

引用Marc R Hoffman on Jacoco Github：

“您的代码使用assert关键字，这将导致一个静态的初始值设定项：

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难题：

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

它引发AssertionError，但是@Generated注释满足了代码覆盖率的要求。但是，这是一种解决方法。解决方案是等待Jacoco在字节码中提供所需的断言过滤。

Filtering assertions is a work in progress。