0

I am creating a Colatz chain in Java but currently, my function is getting an assertion failed error expected not <null> when running. Within my file, I have one public class,

public class Chain {
public Block head;

I have one constructor,

    public Chain() {                                                        
    head = null;

I also have one public string:

public String toString() {                                                      
    if (head == null) {
        return null;
    }
    return head.toString();
}

and the function below is my helper function which I am using to create my chain.

    public void helper_1(Block b, int id, int rank) {
    b = new Block(id, rank);
    int next_id;
    if (id == 1)
        return;
    else if (id % 2 == 0) {
        next_id = id / 2;
    } else
        next_id = 3 * id + 1;

    helper_1(b.next, next_id, rank + 1);

}

And then using this function to get the values created by the helper for testing.

    public Block createChain(int id) {
    if (id <= 0)
        return null;
    helper_1(head, id, 1);
    return head;
}

My Tests are here below that I have been using:

@Test
@Order(5)
@Graded(description = "Chain - testCreateChain", marks = 11)
public void testCreateChain() {
    Chain c = new Chain();
    assertNull(c.createChain(0));
    assertNull(c.createChain(-5));
    
    assertNotNull(ten.head);
    assertEquals(10, ten.head.id);
    assertEquals("(10, 1) -> (5, 2) -> (16, 3) -> (8, 4) -> (4, 5) -> (2, 6) -> (1, 7)", ten.toString());
    assertEquals(10, ten.head.id);
    
    assertEquals("(10, 1) -> (5, 2) -> (16, 3) -> (8, 4) -> (4, 5) -> (2, 6) -> (1, 7)", ten.toString());
    assertEquals("(6, 1) -> (3, 2) -> (10, 3) -> (5, 4) -> (16, 5) -> (8, 6) -> (4, 7) -> (2, 8) -> (1, 9)",
            six.toString());
    assertEquals(
            "(7, 1) -> (22, 2) -> (11, 3) -> (34, 4) -> (17, 5) -> (52, 6) -> (26, 7) -> (13, 8) -> (40, 9) -> (20, 10) -> (10, 11) -> (5, 12) -> (16, 13) -> (8, 14) -> (4, 15) -> (2, 16) -> (1, 17)",
            seven.toString());

    c = new Chain();
    assertEquals(
            "(12, 1) -> (6, 2) -> (3, 3) -> (10, 4) -> (5, 5) -> (16, 6) -> (8, 7) -> (4, 8) -> (2, 9) -> (1, 10)",
            c.createChain(12).toString());
    assertEquals(
            "(12, 1) -> (6, 2) -> (3, 3) -> (10, 4) -> (5, 5) -> (16, 6) -> (8, 7) -> (4, 8) -> (2, 9) -> (1, 10)",
            c.toString());
    
    
    currentMethodName = new Throwable().getStackTrace()[0].getMethodName();
}

This is the error that I am getting:

org.opentest4j.AssertionFailedError: expected: not <null>
at org.junit.jupiter.api.AssertionUtils.fail(AssertionUtils.java:39)
at org.junit.jupiter.api.Assertions.fail(Assertions.java:134)
at org.junit.jupiter.api.AssertNotNull.failNull(AssertNotNull.java:47)
at org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:36)
at org.junit.jupiter.api.AssertNotNull.assertNotNull(AssertNotNull.java:31)
at org.junit.jupiter.api.Assertions.assertNotNull(Assertions.java:300)
at attempts.UnitTest.testCreateChain(UnitTest.java:262)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:77)
at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:568)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:725)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:131)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:149)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:140)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:84)
at org.junit.jupiter.engine.execution.ExecutableInvoker$ReflectiveInterceptorCall.lambda$ofVoidMethod$0(ExecutableInvoker.java:115)
at org.junit.jupiter.engine.execution.ExecutableInvoker.lambda$invoke$0(ExecutableInvoker.java:105)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$InterceptedInvocation.proceed(InvocationInterceptorChain.java:106)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:64)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:45)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:37)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:104)
at org.junit.jupiter.engine.execution.ExecutableInvoker.invoke(ExecutableInvoker.java:98)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.lambda$invokeTestMethod$7(TestMethodTestDescriptor.java:214)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:210)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:66)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:151)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at java.base/java.util.ArrayList.forEach(ArrayList.java:1511)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:41)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$6(NodeTestTask.java:155)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:141)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:137)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$9(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:138)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:95)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:35)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:95)
at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:91)
at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:60)
at org.eclipse.jdt.internal.junit5.runner.JUnit5TestReference.run(JUnit5TestReference.java:98)
at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:40)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:529)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:756)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:452)
at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:210)
yshavit
  • 41,077
  • 7
  • 83
  • 120
jimbo mugwug
  • 11
  • 2
  • 1
    The stack trace says it's from `assertNotNull`, and the only time you call that in your test is `assertNotNull(ten.head)`. We know `ten` isn't null (otherwise, getting its `head` instance would result in a NullPointerException, so its `head` is null. But you haven't shown where you declare or initialize `ten`, so we can't see what's going on, other than the trivial observation that your constructor initializes `head` to null. The code you've shown never sets `head` to anything other than null, so it's not clear to me why you expect it to be non-null. – yshavit Jun 05 '22 at 03:01
  • Does this answer your question? [What is a NullPointerException, and how do I fix it?](https://stackoverflow.com/questions/218384/what-is-a-nullpointerexception-and-how-do-i-fix-it) – tgdavies Jun 05 '22 at 04:00

0 Answers0