How to test functions that throw exceptions?

Question

Aryan Kumar · Answer

To test functions that throw exceptions, you can use the following steps:

Create a test case class for the function you want to test.
In the test case class, create a test method for each exception that the function can throw.
In each test method, call the function and assert that it throws the expected exception.

For example, the following code shows how to test a function that throws an ArithmeticException if the denominator of a division operation is zero:

Java

import org.junit.Test;

public class MyFunctionTest {

  @Test
  public void testDivisionByZero() {
    // Arrange
    int numerator = 10;
    int denominator = 0;

    // Act
    try {
      myFunction(numerator, denominator);
    } catch (ArithmeticException e) {
      // Assert
      assertTrue(e.getMessage().contains("Division by zero"));
    }
  }

  private void myFunction(int numerator, int denominator) {
    if (denominator == 0) {
      throw new ArithmeticException("Division by zero");
    }
  }
}

In this code, the testDivisionByZero() method first sets up the test by creating two variables, numerator and denominator. numerator is set to 10 and denominator is set to 0. The method then calls the myFunction() function, which is the function that is being tested. The myFunction() function throws an ArithmeticException if the denominator is zero. The testDivisionByZero() method catches the ArithmeticException and asserts that the message of the exception contains the string "Division by zero".

This is just one example of how you can test functions that throw exceptions. There are many other ways to do this, and the best way will depend on the specific function that you are testing.

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How to test functions that throw exceptions?

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