java lang exception no runnable methods

In Java, the java lang exception no runnable methods error is basically an exception of Junit, which occurs when Junit is unable to find the runnable test methods. In the spring boot, i.e., one of the most used Java frameworks throws the no runnable methods exception where no runnable test methods are configured in the test classes of Junit.

The Junit framework plays a vital role in the testing of the Java classes. In the past decade, the Junit test methods are determined by the method signature. In the early version of the Junit framework, it searches for the methods which start with the keyword "test". In order to perform the unit test of the Java source code, it runs all the methods in the test class that start with "test".

In the current version of the Junit framework, it searches all the methods that are configured with @Test annotation, not the methods which are starting with the keyword "test".

Let's take an example and try to produce the no runnable methods exception. In our example, we will use Java 8, Junit 4.12 for testing our java source code, Maven, i.e., is build and dependency tool, and Eclipse, i.e., IDE for writing the code.

We will create a new maven project using Eclipse IDE tool and add the following dependency in the pom.xml file.

<dependency>
        <groupId>junit</groupId>
        <artifactId>junit</artifactId>
        <version>4.12</version>
</dependency>

Let's create a simple class NoRunnableMethodsExample to test.

NoRunnableMethodsExample.java

package javaTpoint.NoRunnableMethodsExample;

import java.util.StringTokenizer;

public class NoRunableMethodExceptionExample {
	 //create getMax() method to return maximum value  
    public static int getMax(int intArr[]){  
        int maxValue = 0;  
        for(int i=1; i<intArr.length; i++){  
            if(maxValue < intArr[i])  
            	maxValue = intArr[i];  
        }  
        return maxValue;  
    }  
    //create getCube() method to get the cube of the number  
    public static int getCube(int number){  
        return number*number*number;  
    }  
    //create reverseWord() method to get the reverse of the given string 
    public static String reverseWord(String str){  
  
        StringBuilder newStr = new StringBuilder();  
        StringTokenizer tokenizer = new StringTokenizer(str," ");  
  
        while(tokenizer.hasMoreTokens()){  
        StringBuilder strbuilder = new StringBuilder();
        strbuilder.append(tokenizer.nextToken());  
        strbuilder.reverse();  
  
        newStr.append(strbuilder);  
        newStr.append(" ");  
        }  
        return newStr.toString();  
    }  
}

Now, we write the test class for the above class without defining the test method in the following way:

NoRunnableMethodsExampleTest.java

package javaTpoint.NoRunnableMethodsExample;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.runner.RunWith;
import org.junit.runners.Suite.SuiteClasses;
import org.junit.runners.Suite;

@RunWith(Suite.class)
@SuiteClasses({NoRunableMethodExceptionExample.class})
public class NoRunnableMethodExceptionTest {
	@BeforeClass  
    public static void setBeforeClass() throws Exception {  
        System.out.println("setBeforeClass() method call.");  
    }  
    @Before  
    public void setBefore() throws Exception {  
        System.out.println("setBefore() method call.");  
    }
    @After  
    public void setAfter() throws Exception {  
        System.out.println("setAfter() method call.");  
    }  
  
    @AfterClass  
    public static void setAfterClass() throws Exception {  
        System.out.println("setAfterClass() method call.");  
    }  
}

Now, if we try to run the test class, it will definitely throw the no runnable methods exception.

Output

Resolve exception error

In order to remove the exception, we have to define the runnable methods that call the method of our mains class to check whether they return the expected result or not. We modify the NoRunnableMethodExceptionTest.java class in the following way:

NoRunnableMethodsExampleTest.java

package javaTpoint.NoRunnableMethodsExample;

import static org.junit.Assert.assertEquals;

import org.junit.After;
import org.junit.AfterClass;
import org.junit.Before;
import org.junit.BeforeClass;
import org.junit.Test;

public class NoRunnableMethodExceptionTest {
	@BeforeClass  
    public static void setBeforeClass() throws Exception {  
        System.out.println("setBeforeClass() method call.");  
    }  
    @Before  
    public void setBefore() throws Exception {  
        System.out.println("setBefore() method call.");  
    }
    @Test  
    public void testGetMax(){  
        System.out.println("test case find max");  
        assertEquals(4,NoRunableMethodExceptionExample.getMax(new int[]{1,3,4,2}));  
        assertEquals(0, NoRunableMethodExceptionExample.getMax(new int[]{-12,-3,-4,-2}));  
    }  
    @Test  
    public void testGetCube(){  
        System.out.println("test case cube");  
        assertEquals(27,NoRunableMethodExceptionExample.getCube(3));  
    }  
    @Test  
    public void testReverseWord(){  
        System.out.println("test case reverse word");
        assertEquals("ym eman si nahk ",NoRunableMethodExceptionExample.reverseWord("my name is khan"));  
    }

    @After  
    public void setAfter() throws Exception {  
        System.out.println("setAfter() method call.");  
    }  
  
    @AfterClass  
    public static void setAfterClass() throws Exception {  
        System.out.println("setAfterClass() method call.");  
    }  
}

Output

Conclusion

So, the java lang exception no runnable methods exception throws by the Junit when it founds no test methods to run. We can easily solve the exception by either defining method that starts with the test or use the @Test annotation on the method.

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