Assertions in TestNG
1. What Are Assertions in TestNG?
Assertions are checks you place in your test methods to verify that the application under test behaves as expected. If an assertion fails, TestNG marks the test as FAILED and (for hard asserts) aborts execution of the current method.
2. Syntax for TestNG Assertions
TestNG provides two main assertion styles:
- Hard Asserts via the static methods in org.testng.Assert:
Assert.assertTrue(condition);
Assert.assertEquals(actual, expected);
Assert.assertNotNull(object);- Soft Asserts via an instance of org.testng.asserts.SoftAssert:
SoftAssert soft = new SoftAssert();
soft.assertTrue(condition);
// … more soft asserts …
soft.assertAll(); // must call at end to report failures3. How to Use Assertions in TestNG
import org.testng.Assert;
import org.testng.annotations.Test;
public class AssertionExamples {
@Test
public void hardAssertionTest() {
int sum = 2 + 2;
Assert.assertEquals(sum, 4);
String text = "hello";
Assert.assertTrue(text.startsWith("h"));
}
}Each failed hard-assert immediately stops that test method and marks it failed.
4. Using Messages as a Parameter in TestNG Asserts
You can supply a custom failure message to make reports more descriptive:
@Test
public void todayDateTest() {
String today = getCurrentDate();
// if this assertion fails, “Date format is wrong” appears in the report
Assert.assertEquals(today, "2025-07-05", "Date format is wrong");
}5. Different Types of Asserts in TestNG
Hard Asserts (org.testng.Assert): stop execution on failure.
Soft Asserts (org.testng.asserts.SoftAssert): collect failures and continue; only fail at the final assertAll().
5.1 Hard Asserts
| Method | Fails If… |
|---|---|
| Assert.assertTrue(cond) | cond is false |
| Assert.assertFalse(cond) | cond is true |
| Assert.assertEquals(actual, expected) | objects/values aren’t equal |
| Assert.assertNotEquals(a, b) | objects/values are equal |
| Assert.assertNull(obj) | obj is not null |
| Assert.assertNotNull(obj) | obj is null |
| Assert.fail(“message”) | unconditionally marks test as failed |
5.2 Soft Asserts
import org.testng.annotations.Test;
import org.testng.asserts.SoftAssert;
public class SoftAssertExample {
@Test
public void multipleChecks() {
SoftAssert soft = new SoftAssert();
soft.assertTrue(isElementVisible(), "Element should be visible");
soft.assertEquals(getTitle(), "Dashboard", "Title mismatch");
soft.assertNotNull(getUser(), "User should be logged in");
// Reports any failures above; must call or test passes regardless
soft.assertAll();
}
private boolean isElementVisible() { /*…*/ return false; }
private String getTitle() { /*…*/ return ""; }
private Object getUser() { /*…*/ return null; }
}Even if the first two soft.assert… fail, the method continues through all checks.
soft.assertAll() at the end aggregates and reports all failures at once.
6. Commonly Used TestNG Assert Methods
// org.testng.Assert
Assert.assertTrue(condition, "Optional failure message");
Assert.assertFalse(condition, "Optional failure message");
Assert.assertEquals(actual, expected, "Optional failure message");
Assert.assertNotEquals(actual, expected, "Optional failure message");
Assert.assertNull(object, "Optional failure message");
Assert.assertNotNull(object, "Optional failure message");
Assert.fail("Explicit failure with message");
// org.testng.asserts.SoftAssert
SoftAssert soft = new SoftAssert();
soft.assertTrue(...);
soft.assertFalse(...);
soft.assertEquals(...);
soft.assertAll();
By choosing hard asserts for critical checkpoints (fail fast) and soft asserts when you want to collect multiple verification results in one test, you can make your TestNG suites both robust and informative.
