How to use Hamcrest for testing? Sometime back I’ve written a Hello World JUnit Article with all details. In this tutorial we will go over steps on how to use Hamcrest to create JUnit for your Java project.
Hamcrest is a testing framework for Java with matchers bundled with the JUnit framework to create more readable Java unit tests. I tried it today and I absolutely love it. Very simple and complete documentation makes it perfect.
If you have any of below questions then you are at right place:
- Writing JUnit test cases in Java using Eclipse
- How to write junit test cases in Java
- Sample JUnit test cases in Java
- Writing JUnit test cases using
Hamcrest Matchers - The Benefits of
assertThat vs AssertMethods in JUnit Tests - hamcrest
assertthat()tutorial
Let’s get started:
Create Java class CrunchifyHemcrestJUnitTest.java in Eclipse. We are going to create 4 different category of tests.
- Create JUnit testcases for
Java List - Create JUnit testcases for Java Map
- Create JUnit testcases for Java Object
- Create JUnit testcases for Null Check
Here are the top Hamcrest matchers:
- is()
- hasItems()
- hasSize()
- contains()
- containsInAnyOrder()
Below tutorial covers almost all matchers testcases which will pass all the time. Just modify to create false positive and so on.
You need to add below maven dependency in your project.
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<dependency> <groupId>org.hamcrest</groupId> <artifactId>hamcrest-all</artifactId> <version>1.3</version> </dependency> |
Just add this to pom.xml file. If you don’t see pom.xml then follow this tutorial.
Here is a complete Java code
Just right click on a class and Run As -> JUnit Test.
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package crunchify.com.tutorial; import static org.hamcrest.CoreMatchers.hasItems; import static org.hamcrest.CoreMatchers.is; import static org.hamcrest.CoreMatchers.not; import static org.hamcrest.CoreMatchers.notNullValue; import static org.hamcrest.CoreMatchers.nullValue; import static org.hamcrest.MatcherAssert.assertThat; import static org.hamcrest.Matchers.hasProperty; import static org.hamcrest.collection.IsCollectionWithSize.hasSize; import static org.hamcrest.collection.IsIterableContainingInAnyOrder.containsInAnyOrder; import static org.hamcrest.collection.IsIterableContainingInOrder.contains; import java.util.ArrayList; import java.util.Arrays; import java.util.HashMap; import java.util.List; import java.util.Map; import java.util.Objects; import org.hamcrest.collection.IsEmptyCollection; import org.hamcrest.collection.IsMapContaining; import org.hamcrest.core.IsNull; import org.junit.Test; /** * @author Crunchify.com * * Hamcrest JUnit Tutorials by Crunchify.com * 1. Create JUnit testcases for Java List * 2. Create JUnit testcases for Java Map * 3. Create JUnit testcases for Java Object * 4. Create JUnit testcases for Null Check * */ public class CrunchifyHamcrestJUnitTest { // Testcase-1: JUnit for List @Test public void crunchifyListJUnitTests() { List<String> company = Arrays.asList("Crunchify.com", "Google.com", "Facebook.com"); List<String> crunchifyCompany = Arrays.asList("Crunchify.com", "Google.com", "Facebook.com"); log("\n~~~~~~~~~~~JUnit List Check Test~~~~~~~~~~~"); log("1) assertThat(company, is(crunchifyCompany)) check"); // A shortcut to the frequently used is(equalTo(x)). assertThat(company, is(crunchifyCompany)); log("2) .hasItems() check"); assertThat(company, hasItems("Crunchify.com")); log("3) .hasSize() check"); assertThat(company, hasSize(3)); assertThat(company.size(), is(3)); log("4) .contains() and .containsInAnyOrder() check"); assertThat(company, contains("Crunchify.com", "Google.com", "Facebook.com")); assertThat(company, containsInAnyOrder("Google.com", "Crunchify.com", "Facebook.com")); // FAIL // assertThat(company, contains("Google.com", "Crunchify.com", "Facebook.com")); log("5) .empty() check"); assertThat(company, not(IsEmptyCollection.empty())); assertThat(new ArrayList<>(), IsEmptyCollection.empty()); } private void log(String crunchifyText) { System.out.println(crunchifyText); } @Test public void crunchifyMapJUnitTests() { Map<String, String> company = new HashMap<>(); company.put("C", "Crunchify.com"); company.put("G", "Google.com"); company.put("F", "Facebook.com"); Map<String, String> crunchifyCompany = new HashMap<>(); crunchifyCompany.put("C", "Crunchify.com"); crunchifyCompany.put("G", "Google.com"); crunchifyCompany.put("F", "Facebook.com"); log("\n~~~~~~~~~~~JUnit Map Check Test - All tests will PASS in our example~~~~~~~~~~~"); log("1) assertThat(company, is(crunchifyCompany) check"); assertThat(company, is(crunchifyCompany)); log("2) assertThat(company.size(), is(3)) check"); assertThat(company.size(), is(3)); log("3) .hasEntry() check which creates a matcher for Maps matching at least one entry whose key equals the specified key & value."); assertThat(company, IsMapContaining.hasEntry("C", "Crunchify.com")); assertThat(company, not(IsMapContaining.hasEntry("G", "Twitter.com"))); log("4) .hasKey() creates a matcher for Maps matching at least one key that is equal to the specified key."); assertThat(company, IsMapContaining.hasKey("F")); log("5) .hasValue() creates a matcher for Maps matching at least one key that is equal to the specified value."); assertThat(company, IsMapContaining.hasValue("Crunchify.com")); } @SuppressWarnings("unchecked") @Test public void crunchifyObjectJUnitTests() { List<Company> list = Arrays.asList(new Company("Crunchify", 10), new Company("Google", 30000)); assertThat(list, hasItems(new Company("Crunchify", 10), new Company("Google", 30000))); assertThat(list, containsInAnyOrder(new Company("Google", 30000), new Company("Crunchify", 10))); assertThat(list, containsInAnyOrder(hasProperty("name", is("Google")), hasProperty("name", is("Crunchify")))); log("\n~~~~~~~~~~~JUnit Object Check Test Completed~~~~~~~~~~~"); } // Create Company Object public class Company { public Company(String name, int employeeCount) { this.name = name; this.employeeCount = employeeCount; } private String name; private int employeeCount; public int getEmployeeCount() { return employeeCount; } public void setEmployeeCount(int employeeCount) { this.employeeCount = employeeCount; } public String getName() { return name; } public void setName(String name) { this.name = name; } // Test equal, override equals() and hashCode() @Override public boolean equals(Object c) { if (this == c) return true; if (c == null || getClass() != c.getClass()) return false; Company fruit = (Company) c; return employeeCount == fruit.employeeCount && Objects.equals(name, fruit.name); } @Override public int hashCode() { return Objects.hash(name, employeeCount); } } @Test public void crunchifyNullCheckJUnitTest() { // Two ways to check isNull assertThat(null, is(nullValue())); assertThat(null, is(IsNull.nullValue())); // Two ways to check isNotNull assertThat("crunchify", is(notNullValue())); assertThat("crunchify", is(IsNull.notNullValue())); log("\n~~~~~~~~~~~JUnit Null Check Test Completed~~~~~~~~~~~"); } } |
Eclipse console output:
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~~~~~~~~~~~JUnit Object Check Test Completed~~~~~~~~~~~ ~~~~~~~~~~~JUnit Null Check Test Completed~~~~~~~~~~~ ~~~~~~~~~~~JUnit List Check Test~~~~~~~~~~~ 1) assertThat(company, is(crunchifyCompany)) check 2) .hasItems() check 3) .hasSize() check 4) .contains() and .containsInAnyOrder() check 5) .empty() check ~~~~~~~~~~~JUnit Map Check Test - All tests will PASS in our example~~~~~~~~~~~ 1) assertThat(company, is(crunchifyCompany) check 2) assertThat(company.size(), is(3)) check 3) .hasEntry() check which creates a matcher for Maps matching at least one entry whose key equals the specified key & value. 4) .hasKey() creates a matcher for Maps matching at least one key that is equal to the specified key. 5) .hasValue() creates a matcher for Maps matching at least one key that is equal to the specified value. |
