junit interview questions
Top junit frequently asked interview questions
Does anybody know why JUnit 4 provides assertEquals(foo,bar) but not assertNotEqual(foo,bar) methods?
It provides assertNotSame (corresponding to assertSame) and assertFalse (corresponding to assertTrue), so it seems strange that they didn't bother including assertNotEqual.
By the way, I know that JUnit-addons provides the methods I'm looking for. I'm just asking out of curiosity.
Source: (StackOverflow)
I'm looking for a JSON paring library that supports comparing two JSON objects ignoring child order, specifically for unit testing JSON returning from a web service against an expected value.
Do any of the major JSON libraries support this? the org.json simply does a reference comparison.
Source: (StackOverflow)
I want to execute test methods which are annotated by @Test in specific order.
For example:
public class MyTest {
@Test public void test1(){}
@Test public void test2(){}
}
I want to ensure to run test1() before test2() each time I run MyTest, but I couldn't find annotation like @Test(order=xx).
I think it's quite important feature for JUnit, if author of JUnit doesn't want the order feature, why?
Source: (StackOverflow)
I have a maven program, it compiles fine. When I run mvn test it does not run any tests (under TESTs header says There are no tests to run.).
I've recreated this problem with a super simple setup which I will include below as well as the output when run with -X.
The unit tests run fine from eclipse (both with its default junit package and when I instead include the junit.jar downloaded by maven). Also mvn test-compile correctly creates the class under test-classes. I am running this on OSX 10.6.7 with Maven 3.0.2 and java 1.6.0_24.
Here is the directory structure:
/my_program/pom.xml
/my_program/src/main/java/ClassUnderTest.java
/my_program/src/test/java/ClassUnderTestTests.java
pom.xml:
<?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/maven-v4_0_0.xsd">
<modelVersion>4.0.0</modelVersion>
<groupId>my_group</groupId>
<artifactId>my_program</artifactId>
<packaging>jar</packaging>
<version>1.0-SNAPSHOT</version>
<name>My Program</name>
<dependencies>
<dependency>
<groupId>junit</groupId>
<artifactId>junit</artifactId>
<version>4.8.1</version>
<scope>test</scope>
</dependency>
</dependencies>
<build>
<plugins>
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-compiler-plugin</artifactId>
<configuration>
<source>1.5</source>
<target>1.5</target>
</configuration>
</plugin>
</plugins>
</build>
</project>
ClassUnderTest.java:
public class ClassUnderTest {
public int functionUnderTest(int n) {
return n;
}
}
ClassUnderTestTests.java:
import org.junit.Assert;
import org.junit.Before;
import org.junit.Test;
public class ClassUnderTestTests {
private ClassUnderTest o;
@Before
public void setUp() {
o = new ClassUnderTest();
}
@Test
public void testFunctionUnderTest_testCase1() {
Assert.assertEquals(1, o.functionUnderTest(1));
}
@Test
public void testFunctionUnderTest_testCase2() {
Assert.assertEquals(2, o.functionUnderTest(2));
}
}
End of mvn -X test:
[DEBUG] Configuring mojo org.apache.maven.plugins:maven-surefire-plugin:2.7.1:test from plugin realm ClassRealm[plugin>org.apache.maven.plugins:maven-surefire-plugin:2.7.1, parent: sun.misc.Launcher$AppClassLoader@5224ee]
[DEBUG] Configuring mojo 'org.apache.maven.plugins:maven-surefire-plugin:2.7.1:test' with basic configurator -->
[DEBUG] (s) basedir = /Users/aaron/Programs/my_program
[DEBUG] (s) childDelegation = false
[DEBUG] (s) classesDirectory = /Users/aaron/Programs/my_program/target/classes
[DEBUG] (s) disableXmlReport = false
[DEBUG] (s) enableAssertions = true
[DEBUG] (s) forkMode = once
[DEBUG] (s) junitArtifactName = junit:junit
[DEBUG] (s) localRepository = id: local
url: file:///Users/aaron/.m2/repository/
layout: none
[DEBUG] (f) parallelMavenExecution = false
[DEBUG] (s) pluginArtifactMap = {org.apache.maven.plugins:maven-surefire-plugin=org.apache.maven.plugins:maven-surefire-plugin:maven-plugin:2.7.1:, org.apache.maven.surefire:surefire-booter=org.apache.maven.surefire:surefire-booter:jar:2.7.1:compile, org.apache.maven.surefire:surefire-api=org.apache.maven.surefire:surefire-api:jar:2.7.1:compile, org.apache.maven.surefire:maven-surefire-common=org.apache.maven.surefire:maven-surefire-common:jar:2.7.1:compile, org.apache.maven.shared:maven-common-artifact-filters=org.apache.maven.shared:maven-common-artifact-filters:jar:1.3:compile, org.codehaus.plexus:plexus-utils=org.codehaus.plexus:plexus-utils:jar:2.0.5:compile, junit:junit=junit:junit:jar:3.8.1:compile, org.apache.maven.reporting:maven-reporting-api=org.apache.maven.reporting:maven-reporting-api:jar:2.0.9:compile}
[DEBUG] (s) printSummary = true
[DEBUG] (s) project = MavenProject: my_group:my_program:1.0-SNAPSHOT @ /Users/aaron/Programs/my_program/pom.xml
[DEBUG] (s) projectArtifactMap = {junit:junit=junit:junit:jar:4.8.1:test}
[DEBUG] (s) redirectTestOutputToFile = false
[DEBUG] (s) remoteRepositories = [ id: central
url: http://repo1.maven.org/maven2
layout: default
snapshots: [enabled => false, update => daily]
releases: [enabled => true, update => never]
]
[DEBUG] (s) reportFormat = brief
[DEBUG] (s) reportsDirectory = /Users/aaron/Programs/my_program/target/surefire-reports
[DEBUG] (s) session = org.apache.maven.execution.MavenSession@dfbb43
[DEBUG] (s) skip = false
[DEBUG] (s) skipTests = false
[DEBUG] (s) testClassesDirectory = /Users/aaron/Programs/my_program/target/test-classes
[DEBUG] (s) testFailureIgnore = false
[DEBUG] (s) testNGArtifactName = org.testng:testng
[DEBUG] (s) testSourceDirectory = /Users/aaron/Programs/my_program/src/test/java
[DEBUG] (s) trimStackTrace = true
[DEBUG] (s) useFile = true
[DEBUG] (s) useManifestOnlyJar = true
[DEBUG] (s) workingDirectory = /Users/aaron/Programs/my_program
[DEBUG] -- end configuration --
[INFO] Surefire report directory: /Users/aaron/Programs/my_program/target/surefire-reports
[DEBUG] Setting system property [user.dir]=[/Users/aaron/Programs/my_program]
[DEBUG] Setting system property [localRepository]=[/Users/aaron/.m2/repository]
[DEBUG] Setting system property [basedir]=[/Users/aaron/Programs/my_program]
[DEBUG] Using JVM: /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/java
[DEBUG] Using manager EnhancedLocalRepositoryManager with priority 10 for /Users/aaron/.m2/repository
[DEBUG] dummy:dummy:jar:1.0 (selected for null)
[DEBUG] org.apache.maven.surefire:surefire-booter:jar:2.7.1:compile (selected for compile)
[DEBUG] org.apache.maven.surefire:surefire-api:jar:2.7.1:compile (selected for compile)
[DEBUG] Adding to surefire booter test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-booter/2.7.1/surefire-booter-2.7.1.jar Scope: compile
[DEBUG] Adding to surefire booter test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-api/2.7.1/surefire-api-2.7.1.jar Scope: compile
[DEBUG] Using manager EnhancedLocalRepositoryManager with priority 10 for /Users/aaron/.m2/repository
[DEBUG] dummy:dummy:jar:1.0 (selected for null)
[DEBUG] org.apache.maven.surefire:surefire-junit4:jar:2.7.1:test (selected for test)
[DEBUG] org.apache.maven.surefire:surefire-api:jar:2.7.1:test (selected for test)
[DEBUG] Adding to surefire test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-junit4/2.7.1/surefire-junit4-2.7.1.jar Scope: test
[DEBUG] Adding to surefire test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-api/2.7.1/surefire-api-2.7.1.jar Scope: test
[DEBUG] Test Classpath :
[DEBUG] /Users/aaron/Programs/my_program/target/test-classes
[DEBUG] /Users/aaron/Programs/my_program/target/classes
[DEBUG] /Users/aaron/.m2/repository/junit/junit/4.8.1/junit-4.8.1.jar
[DEBUG] Using manager EnhancedLocalRepositoryManager with priority 10 for /Users/aaron/.m2/repository
[DEBUG] dummy:dummy:jar:1.0 (selected for null)
[DEBUG] org.apache.maven.surefire:surefire-booter:jar:2.7.1:compile (selected for compile)
[DEBUG] org.apache.maven.surefire:surefire-api:jar:2.7.1:compile (selected for compile)
[DEBUG] Adding to surefire booter test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-booter/2.7.1/surefire-booter-2.7.1.jar Scope: compile
[DEBUG] Adding to surefire booter test classpath: /Users/aaron/.m2/repository/org/apache/maven/surefire/surefire-api/2.7.1/surefire-api-2.7.1.jar Scope: compile
Forking command line: /bin/sh -c cd /Users/aaron/Programs/my_program && /System/Library/Java/JavaVirtualMachines/1.6.0.jdk/Contents/Home/bin/java -jar /Users/aaron/Programs/my_program/target/surefire/surefirebooter6118081963679415631.jar /Users/aaron/Programs/my_program/target/surefire/surefire4887918564882595612tmp /Users/aaron/Programs/my_program/target/surefire/surefire9012255138269731406tmp
-------------------------------------------------------
T E S T S
-------------------------------------------------------
There are no tests to run.
Results :
Tests run: 0, Failures: 0, Errors: 0, Skipped: 0
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESS
[INFO] ------------------------------------------------------------------------
[INFO] Total time: 2.089s
[INFO] Finished at: Mon May 30 12:03:09 EDT 2011
[INFO] Final Memory: 7M/62M
[INFO] ------------------------------------------------------------------------
Source: (StackOverflow)
OK, so the @Ignore annotation is good for marking that a test case shouldn't be run.
However, sometimes I want to ignore a test based on runtime information. An example might be if I have a concurrency test that needs to be run on a machine with a certain number of cores. If this test were run on a uniprocessor machine, I don't think it would be correct to just pass the test (since it hasn't been run), and it certainly wouldn't be right to fail the test and break the build.
So I want to be able to ignore tests at runtime, as this seems like the right outcome (since the test framework will allow the build to pass but record that the tests weren't run). I'm fairly sure that the annotation won't give me this flexibility, and suspect that I'll need to manually create the test suite for the class in question. However, the documentation doesn't mention anything about this and looking through the API it's also not clear how this would be done programmatically (i.e. how do I programatically create an instance of Test or similar that is equivalent to that created by the @Ignore annotation?).
If anyone has done something similar in the past, or has a bright idea of how else I could go about this, I'd be happy to hear about it.
Source: (StackOverflow)
Is there a way to set my own custom test case names when using parameterized tests in JUnit4?
I'd like to change the default — [Test class].runTest[n] — to something meaningful.
Source: (StackOverflow)
I need to write JUnit tests for an old application that's poorly designed and is writing a lot of error messages to standard output. When the getResponse(String request) method behaves correctly it returns a XML response:
@BeforeClass
public static void setUpClass() throws Exception {
Properties queries = loadPropertiesFile("requests.properties");
Properties responses = loadPropertiesFile("responses.properties");
instance = new ResponseGenerator(queries, responses);
}
@Test
public void testGetResponse() {
String request = "<some>request</some>";
String expResult = "<some>response</some>";
String result = instance.getResponse(request);
assertEquals(expResult, result);
}
But when it gets malformed XML or does not understand the request it returns null and writes some stuff to standard output.
Is there any way to assert console output in JUnit? To catch cases like:
System.out.println("match found: " + strExpr);
System.out.println("xml not well formed: " + e.getMessage());
Source: (StackOverflow)
I would like to inject a Mockito mock object into a Spring (3+) bean for the purposes of unit testing with JUnit. My bean dependencies are currently injected by using the @Autowired annotation on private member fields.
I have considered using ReflectionTestUtils.setField but the bean instance that I wish to inject is actually a proxy and hence does not declare the private member fields of the target class. I do not wish to create a public setter to the dependency as I will then be modifying my interface purely for the purposes of testing.
I have followed some advice given by the Spring community but the mock does not get created and the auto-wiring fails:
<bean id="dao" class="org.mockito.Mockito" factory-method="mock">
<constructor-arg value="com.package.Dao" />
</bean>
The error I currently encounter is as follows:
...
Caused by: org...NoSuchBeanDefinitionException:
No matching bean of type [com.package.Dao] found for dependency:
expected at least 1 bean which qualifies as autowire candidate for this dependency.
Dependency annotations: {
@org...Autowired(required=true),
@org...Qualifier(value=dao)
}
at org...DefaultListableBeanFactory.raiseNoSuchBeanDefinitionException(D...y.java:901)
at org...DefaultListableBeanFactory.doResolveDependency(D...y.java:770)
If I set the constructor-arg value to something invalid no error occurs when starting the application context.
Source: (StackOverflow)
When I attempt to run the following test in IntelliJ IDEA I get the message:
!!! JUnit version 3.8 or later expected:
It should be noted that this is an Android project I am working on in IntelliJ IDEA 9.
public class GameScoreUtilTest {
@Test
public void testCalculateResults() throws Exception {
final Game game = new Game();
final Player player1 = new Player();
{
final PlayedHole playedHole = new PlayedHole();
playedHole.setScore(1);
game.getHoleScoreMap().put(player1, playedHole);
}
{
final PlayedHole playedHole = new PlayedHole();
playedHole.setScore(3);
game.getHoleScoreMap().put(player1, playedHole);
}
final GameResults gameResults = GameScoreUtil.calculateResults(game);
assertEquals(4, gameResults.getScore());
}
}
The full stack trace looks like this...
!!! JUnit version 3.8 or later expected:
java.lang.RuntimeException: Stub!
at junit.runner.BaseTestRunner.<init>(BaseTestRunner.java:5)
at junit.textui.TestRunner.<init>(TestRunner.java:54)
at junit.textui.TestRunner.<init>(TestRunner.java:48)
at junit.textui.TestRunner.<init>(TestRunner.java:41)
at com.intellij.rt.execution.junit.JUnitStarter.junitVersionChecks(JUnitStarter.java:152)
at com.intellij.rt.execution.junit.JUnitStarter.canWorkWithJUnitVersion(JUnitStarter.java:136)
at com.intellij.rt.execution.junit.JUnitStarter.main(JUnitStarter.java:49)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
at java.lang.reflect.Method.invoke(Method.java:597)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:110)
Process finished with exit code -3
Source: (StackOverflow)
I feel like an idiot for asking this but I've wasted way too much time on this already.
I'm an old Eclipse user which makes starting a java project with JUnit obvious. Just start writing a test class and it offers to add any libraries and imports that the file needs.
I decided to try out IntelliJ this morning so downloaded the trial. The JUnit plugin is installed. I make a new Java project and I want to write a test case.
How do I add the junit.jar to my project? (I actually want to add it to every java project, now and forever more - is there a way of doing that?).
Source: (StackOverflow)
I know that == has some issues when comparing two Strings. It seems that String.equals() is a better approach. Well, I'm doing JUnit testing and my inclination is to use assertEquals(str1, str2). Is this a reliable way to assert two Strings contain the same content? I would use assertTrue(str1.equals(str2)), but then you don't get the benefit of seeing what the expected and actual values are on failure.
On a related note, does anyone have a link to a page or thread that plainly explains the problems with str1 == str2?
Thanks!
Source: (StackOverflow)
I'm using JUnit-dep 4.10 and Hamcrest 1.3.RC2.
I've created a custom matcher that looks like the following:
public static class MyMatcher extends TypeSafeMatcher<String> {
@Override
protected boolean matchesSafely(String s) {
/* implementation */
}
@Override
public void describeTo(Description description) {
/* implementation */
}
@Override
protected void describeMismatchSafely(String item, Description mismatchDescription) {
/* implementation */
}
}
It works perfectly fine when run from the command line using Ant. But when run from IntelliJ, it fails with:
java.lang.NoSuchMethodError: org.hamcrest.Matcher.describeMismatch(Ljava/lang/Object;Lorg/hamcrest/Description;)V
at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:18)
at org.hamcrest.MatcherAssert.assertThat(MatcherAssert.java:8)
at com.netflix.build.MyTest.testmyStuff(MyTest.java:40)
My guess is that it's using the wrong hamcrest.MatcherAssert. How do I find which hamcrest.MatcherAssert it's using (ie which jar file it's using for hamcrest.MatcherAssert)? AFAICT, the only hamcrest jars in my classpath is 1.3.RC2.
Is IntelliJ IDEA using it's own copy of JUnit or Hamcrest?
How do I output the runtime CLASSPATH that IntelliJ is using?
Source: (StackOverflow)
In JUnit 3, I could get the name of the currently running test like this:
public class MyTest extends TestCase
{
public void testSomething()
{
System.out.println("Current test is " + getName());
...
}
}
which would print "Current test is testSomething".
Is there any out-of-the-box or simple way to do this in JUnit 4?
Background: Obviously, I don't want to just print the name of the test. I want to load test-specific data that is stored in a resource with the same name as the test. You know, convention over configuration and all that.
Thanks!
Source: (StackOverflow)