Mockito mock method throwing exception - mockito

Question

I'm trying to mock a class using mock() method; however, it is throwing an exception when I call it.
Here is my code for test class:
#Test
#DisplayName("Function should return when pass in null componentResource")
public void passinNullResourceDoesNotChangeList() {
FormHelper formMock = mock(FormHelper.class);
boolean persisChanges = false;
List<Map<String, String>> listArg = new ArrayList<>();
Map<String, String> filler = new HashMap<>();
filler.put("Hello", "World");
listArg.add(filler);
List<Map<String, String>> expected = new ArrayList<>(listArg);
formMock.readMultiProperty(null, listArg, persisChanges);
assertThat(listArg, is(expected));
}
Here is the FormHelper class:
private FormHelper() {
}
/**
* Reads the values of the "multi" property of the given component resource and optionally attempts to save it in the new format if
* needed.
*
* #param componentResource the components resource
* #param items the list of item data from the property
* #param persistChanges if true it will attempt to save the items in the new JSON format when they were in the old '~' separated
* format
*/
public static void readMultiProperty(final Resource componentResource,
final List<Map<String, String>> items,
final boolean persistChanges) {
boolean allowModification = false;
final ValueMap properties = getProperties(componentResource);
if (properties == null) {
return;
} else if (properties instanceof ModifiableValueMap) {
allowModification = true;
}
final String[] multi = properties.get("multi", String[].class);
if (multi != null) {
boolean needsConversion = false;
for (final String item : multi) {
final Map<String, String> itemData = new HashMap<>();
try {
final JSONObject object = new JSONObject(item);
readFromJsonObject(object, itemData);
} catch (JSONException ex) {
needsConversion = true;
readFromSeparatedValue(item, itemData);
}
items.add(itemData);
}
if (allowModification && persistChanges && needsConversion) {
setJsonConvertedValues(componentResource, items);
try {
componentResource.getResourceResolver().commit();
} catch (PersistenceException ex) {
LOGGER.error(String.format(
"Failed to save changes of the form component at %s", componentResource.getPath()), ex);
}
}
}
}
}
Here is the exception it has thrown:
java.lang.ExceptionInInitializerError
at org.mockito.internal.exceptions.stacktrace.ConditionalStackTraceFilter.<init>(ConditionalStackTraceFilter.java:17)
at org.mockito.exceptions.base.MockitoException.filterStackTrace(MockitoException.java:30)
at org.mockito.exceptions.base.MockitoException.<init>(MockitoException.java:19)
at org.mockito.exceptions.misusing.MockitoConfigurationException.<init>(MockitoConfigurationException.java:18)
at org.mockito.internal.configuration.ClassPathLoader.loadImplementations(ClassPathLoader.java:145)
at org.mockito.internal.configuration.ClassPathLoader.findPluginImplementation(ClassPathLoader.java:110)
at org.mockito.internal.configuration.ClassPathLoader.findPlatformMockMaker(ClassPathLoader.java:106)
at org.mockito.internal.configuration.ClassPathLoader.<clinit>(ClassPathLoader.java:59)
at org.mockito.internal.util.MockUtil.<clinit>(MockUtil.java:21)
at org.mockito.internal.MockitoCore.<init>(MockitoCore.java:40)
at org.mockito.Mockito.<clinit>(Mockito.java:932)
at com.iggroup.onedomain.form.FormHelperTest.passinNullResourceDoesNotChangeList(FormHelperTest.java:38)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.junit.platform.commons.util.ReflectionUtils.invokeMethod(ReflectionUtils.java:675)
at org.junit.jupiter.engine.execution.MethodInvocation.proceed(MethodInvocation.java:60)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain$ValidatingInvocation.proceed(InvocationInterceptorChain.java:125)
at org.junit.jupiter.engine.extension.TimeoutExtension.intercept(TimeoutExtension.java:132)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestableMethod(TimeoutExtension.java:124)
at org.junit.jupiter.engine.extension.TimeoutExtension.interceptTestMethod(TimeoutExtension.java:74)
at org.junit.jupiter.engine.execution.ExecutableInvoker$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:104)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.proceed(InvocationInterceptorChain.java:62)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.chainAndInvoke(InvocationInterceptorChain.java:43)
at org.junit.jupiter.engine.execution.InvocationInterceptorChain.invoke(InvocationInterceptorChain.java:35)
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$6(TestMethodTestDescriptor.java:202)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.invokeTestMethod(TestMethodTestDescriptor.java:198)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:135)
at org.junit.jupiter.engine.descriptor.TestMethodTestDescriptor.execute(TestMethodTestDescriptor.java:69)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:135)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.util.ArrayList.forEach(ArrayList.java:1259)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at java.util.ArrayList.forEach(ArrayList.java:1259)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.invokeAll(SameThreadHierarchicalTestExecutorService.java:38)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$5(NodeTestTask.java:139)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$7(NodeTestTask.java:125)
at org.junit.platform.engine.support.hierarchical.Node.around(Node.java:135)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.lambda$executeRecursively$8(NodeTestTask.java:123)
at org.junit.platform.engine.support.hierarchical.ThrowableCollector.execute(ThrowableCollector.java:73)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.executeRecursively(NodeTestTask.java:122)
at org.junit.platform.engine.support.hierarchical.NodeTestTask.execute(NodeTestTask.java:80)
at org.junit.platform.engine.support.hierarchical.SameThreadHierarchicalTestExecutorService.submit(SameThreadHierarchicalTestExecutorService.java:32)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestExecutor.execute(HierarchicalTestExecutor.java:57)
at org.junit.platform.engine.support.hierarchical.HierarchicalTestEngine.execute(HierarchicalTestEngine.java:51)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:229)
at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$6(DefaultLauncher.java:197)
at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:211)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:191)
at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:128)
at com.intellij.junit5.JUnit5IdeaTestRunner.startRunnerWithArgs(JUnit5IdeaTestRunner.java:71)
at com.intellij.rt.junit.IdeaTestRunner$Repeater$1.execute(IdeaTestRunner.java:38)
at com.intellij.rt.execution.junit.TestsRepeater.repeat(TestsRepeater.java:11)
at com.intellij.rt.junit.IdeaTestRunner$Repeater.startRunnerWithArgs(IdeaTestRunner.java:35)
at com.intellij.rt.junit.JUnitStarter.prepareStreamsAndStart(JUnitStarter.java:235)
at com.intellij.rt.junit.JUnitStarter.main(JUnitStarter.java:54)
Caused by: java.lang.NullPointerException
at org.mockito.internal.exceptions.stacktrace.StackTraceFilter.<clinit>(StackTraceFilter.java:21)
... 77 more
The exception is definitely referring to the line where the mock() method is called, but I don't know why.

Answer 1

FormHelper has a private constructor and readMultiProperty is a static method. You cannot use Mockito to mock the static method.
In order to mock the static method, you can use PowerMockito to mock it.
But I don't recommend you to do so. The best way is to avoid using PowerMockito, and design your code to be testable code.
For e.g. in your case, FormHelper can be a singleton service and let's design it to implement an interface.