Question connected to Cyclomatic Complexity

[kanb...@gmail.com]

Hi,

I have a question connected to Cyclomatic Complexity. According the documentation the "Cyclomatic Complexity is the minimum number of paths that can, in (linear) combination, generate all possible paths through a method". There is also a calculation for it v(G) = B - D + 1, but was not sure in my case.

I have simple method what I want to test:

public int increase(int i) {
    if (i > 1) {
        i = i+ 1;
    }
    if (i > 10) {
        i = i+ 1;
    }
    return i;
}

And my test is very simple, I don't do any assertions, just call it with two different numbers:

@Test
void test() {
    increase(100);
    increase(-10);
}

I used the following coverage limit:

<limit>
    <counter>COMPLEXITY</counter>
    <value>COVEREDRATIO</value>
    <minimum>1.00</minimum>
</limit>

So I had the assumption that the coverage report should fail, as I didn't test (call) the method with a number which is 1 < n < 10, but to my surprise the coverage failed.

Do you know why it is passed in my case?

My simplified pom.xml file just in case:

<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
         xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
    <modelVersion>4.0.0</modelVersion>

    <groupId>com.kanbagoly</groupId>
    <artifactId>something</artifactId>
    <version>1.0-SNAPSHOT</version>

    <properties>
        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
        <maven.compiler.source>1.8</maven.compiler.source>
        <maven.compiler.target>1.8</maven.compiler.target>
        <junit.jupiter.version>5.5.2</junit.jupiter.version>
    </properties>

    <dependencies>
        <dependency>
            <groupId>org.junit.jupiter</groupId>
            <artifactId>junit-jupiter</artifactId>
            <version>${junit.jupiter.version}</version>
            <scope>test</scope>
        </dependency>
    </dependencies>

    <build>
        <plugins>
            <plugin>
                <artifactId>maven-compiler-plugin</artifactId>
                <version>3.7.0</version>
            </plugin>
            <plugin>
                <artifactId>maven-surefire-plugin</artifactId>
                <version>2.22.2</version>
            </plugin>
            <plugin>
                <groupId>org.jacoco</groupId>
                <artifactId>jacoco-maven-plugin</artifactId>
                <version>0.8.4</version>
                <executions>
                    <execution>
                        <id>prepare-agent</id>
                        <goals>
                            <goal>prepare-agent</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>report</id>
                        <phase>prepare-package</phase>
                        <goals>
                            <goal>report</goal>
                        </goals>
                    </execution>
                    <execution>
                        <id>check</id>
                        <goals>
                            <goal>check</goal>
                        </goals>
                        <configuration>
                            <rules>
                                <rule>
                                    <element>BUNDLE</element>
                                    <limits>
                                        <limit>
                                            <counter>COMPLEXITY</counter>
                                            <value>COVEREDRATIO</value>
                                            <minimum>1.00</minimum>
                                        </limit>
                                    </limits>
                                </rule>
                            </rules>
                        </configuration>
                    </execution>
                </executions>
            </plugin>

        </plugins>
    </build>

</project>

Thank you for your answer in advance,
Csaba Kerti

[kanb...@gmail.com]

* "So I had the assumption that the coverage report should fail, as I didn't test (call) the method with a number which is 1 < n < 10, but to my surprise the coverage passed."

[Marc Hoffmann]

Hi,

cyclomatic complexity is calculated based on branches. In your case the cyclomativ complexity is 3 and your two test cases cover all branches.

Path coverage is a different metric which is not supported by JaCoCo.

Best regards,

-marc

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[kanb...@gmail.com]

Hi Marc,

Thank you for your quick answer and for helping me to understand it. Do you have a small example when the branch coverage would pass but the cyclomatic complexity would fail?

Thank you,
Csaba

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[Marc Hoffmann]

There is no such example. Cyclomatic complexity coverage is derived from branch coverage.

Cyclomatic complexity coverage is something I invented for JaCoCo. I don’t think there is a official definition for it. Here are the definitions for JaCoCo:

https://www.jacoco.org/jacoco/trunk/doc/counters.html

Regards,

-marc

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