Jacobo code coverage

Original address ：

jacoco Instructions for incremental solutions _dray_ The blog of -CSDN Blog _jacoco The incremental

jacoco: jacoco Second opening , Support incremental code coverage

One 、Jacoco brief introduction ：

 JaCoCo It's an open source Java Code coverage tools .

 JaCoCo Only the coverage of full code is counted , During code iteration , For example, it was modified bug, Another version of the code has been released .JaCoCo The statistics of are cleared , Trigger code coverage needs to be performed from scratch .

This scenario , We just need to test the incremental code , It's time to be right about jacoco Secondary development .

jacoco Count code coverage , Generally, it is combined with automation , such as jacoco Combined with interface automation . At that time, we can also perform it manually case, To count code coverage .

Can be embedded into Ant、Maven in ; It can be used as Eclipse plug-in unit , You can use it JavaAgent Technical monitoring Java Procedures, etc .

Many third-party tools provide access to JaCoCo Integration of , Such as sonar、Jenkins etc. .

Two 、 Code coverage introduction ：

Coverage is used to measure the test of test code to function code . Through statistics, test the lines in the function code 、 Branch 、 Class and other simulation scenarios , To quantify the adequacy of the test .

Code coverage = Code coverage , A measure .

Coverage is simple ： Ran a test case , Those modules in the project code 、 file 、 class 、 Method Yes .

The row coverage is the finest granularity , Other coverage rates can be calculated from the row coverage rate .

2.1 Line overlay

When at least one instruction is specified Source line Execution time , The source line is considered to have been executed .

Generally speaking, it means , Test behavior , Triggered this line of code , Then this line of code is covered .

2.2 Branch coverage

if and switch Statement counts as branch coverage , This indicator calculates the total number of branches in a method , And determine the number of branches executed and not executed .

All uncovered ： All branches are not executed , Red sign

Partial coverage ： Some branches are executed , Yellow sign

Full coverage ： All branches have been executed , Green sign .

2.3 Methods cover

When at least one instruction in the method is executed , The method is considered to have been performed , Including constructors and static initialization methods .

2.4 Code coverage means

Analyze uncovered code , Whether the backstepping test design is sufficient , Whether there are test design blind spots in the code not covered .

2.5 Misunderstanding of coverage

If the code is as follows ：

if (i>100)
    j = 10/i        //  There is no division 0 error 
else
    j = 10/(i+2)    // i==-2, except 0 error 

Cover 2 Branches , Just design i==101 and i==1, But for finding i==-2 This bug There is no effect when clicking .

therefore ：

1、 Don't simply pursue high code coverage

2、 High coverage test cases do not mean that test cases are valid

3、 A branch that is not covered is equivalent to any error on the branch that cannot be found

3、 ... and 、jacoco principle

jacoco Use the method of inserting piles to record the coverage data , Through a probe Probe to inject .

The pile insertion modes are 2 Kind of ：

3.1 on-the-fly Pattern

7、Jacoco Incremental coverage
7.1 Incremental coverage
Incremental coverage ： What code or branches are not covered between two submissions .
Purpose ： Detect the line coverage of the same test case on the code before and after modification
Suppose that the code changes submitted twice are as follows ：
if(x>100)
-    print(1)
+    print(2)
else
-    print(3)
+    print(4)

Each line of code has 3 States ：+、-、 unchanged
Before and after modification , Run the same test case , Each row has 4 States ： Overwrite before modification / Not overwritten before modification , Overwrite after modification / Modified but not overwritten .
So the incremental coverage has 3x4=12 In this case , More important are ： The new code does not cover , The new code covers , Unchanged code is overwritten before modification , Not covered after modification .

7.2 Incremental Application
jacoco Second opening ： https://gitee.com/Dray/jacoco.git
Incremental code acquisition ： https://gitee.com/Dray/dode-diff.git

Usage method ：
1、jacoco client , To collect information