Introduction
Install the Maven JaCoCo plugin.
Insert the following code into pom.xml.
<plugin> <groupId>org.jacoco</groupId> <artifactId>jacoco-maven-plugin</artifactId> <version>0.8.2</version> <executions> <execution> <goals> <goal>prepare-agent</goal> </goals> </execution> <execution> <id>report</id> <phase>test</phase> <goals> <goal>report</goal> </goals> </execution> </executions> </plugin>
Add a Unit Test
Create a class as "StringUtil.java" and add following snippet
package com.zainabed.tutorials;
public class StringUtil {
public int findIntegerCount(String input) {
if (input == null) {
return 0;
}
int count = 0;
for (int index = 0; index < input.length(); index++) {
char character = input.charAt(index);
if (character >= 48 && character <= 57) {
count++;
}
}
return count;
}
}
Next, create a unit test class for above class as "StringUtilTest.java".
package com.zainabed.tutorials;
import org.junit.jupiter.api.Test;
import static org.junit.jupiter.api.Assertions.assertEquals;
class StringUtilTest {
@Test
void should_return_count_of_numeric_value() {
StringUtil stringUtil = new StringUtil();
String input = "1name34sample;";
assertEquals(3, stringUtil.findIntegerCount(input));
input = "namesample";
assertEquals(0, stringUtil.findIntegerCount(input));
}
}
Now execute the maven build. It will generate the code coverage report.
mvn clean install
Code coverage result
You can configure different goals of the JaCoCo plugin, such as restricting code coverage percentage.
Our application has 75% branch coverage so far. Let's use the following snippet to configure the coverage limit by setting the execution configuration of the JaCoCo plugin and setting the value to 80%.
<execution>
<id>coverage-check</id>
<phase>test</phase>
<goals>
<goal>check</goal>
</goals>
<configuration>
<rules>
<rule>
<element>CLASS</element>
<limits>
<limit>
<counter>BRANCH</counter>
<value>COVEREDRATIO</value>
<minimum>80%</minimum>
</limit>
</limits>
</rule>
</rules>
</configuration>
</execution>
Now with this configuration build will fail.
We can make the build pass by improving the branch code coverage. Let us update the unit test as follows.
@Test
void should_return_zero_for_empty_string() {
StringUtil stringUtil = new StringUtil();
assertEquals(0, stringUtil.findIntegerCount(null));
}
Build the application again
mvn clean install
The report will show the following result.
Conclusion
Code coverage is a useful asset to improve unit testing of applications and JaCoCo facilitates it efficiently.
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