如何在Intellij中使用junit自动导入测试方法

Question

I'm trying to learn how to use junit4 for testing in Intellij to practice algorithm questions in CTCI and leetcode. However, when I create the test I need to manually import every method to test, rather than importing the whole class and getting all the methods with it. Here is an example of a class in my src folder:

package leetcode;

public class JewelsAndStones{

  /*Simple brute force method using nested for loops*/

  public static int findJewelsInStonesBruteForce(String J, String S){
    char[] jewelChars = J.toCharArray();
    char[] stoneChars = S.toCharArray();
    int count = 0;
    for (char jewel : jewelChars) {
      for (char stone: stoneChars) {
        if (jewel == stone) {
          count ++;
        }
      }
    }
    return count;
  }
}

and here is the test class located in the test folder:

package leetcode;
import org.junit.*;
import static junit.framework.TestCase.assertEquals;
import static leetcode.JewelsAndStones.findJewelsInStonesBruteForce;


public class JewelsAndStonesTest {

  @Test
  public void testFindJewelsInStones() throws Exception {
    String J = "aA";
    String S = "aaAbbbb";
    assertEquals(3, findJewelsInStonesBruteForce(J,S));
  }
  @Test
  public void testFindJewelsInStonesBadInput() throws Exception {

  }
}

So for a class where I may have 3 different solution methods, do I need to do import static leetcode.JewelsAndStones.*additonalMethodToTest* for every one? using import static leetcode.JewelsAndStones.* or better yet import static leetcode.* does not work.

Answer 1

Set your cursor on the class name, press Alt + Enter and select "Create test" in the pop-up menu. Then check all methods you want to test and Idea will create a test class for you with all methods stubs.

UPD: I'd like to add that there is no reason to make your methods static at all. Just public:

public int findJewelsInStones(String J, String S) {
  ...
}

Then your test code should be something like this:

@Test
public void testFindJewelsInStones() throws Exception {
  // Given
  JewelsAndStones jewelAndStones = new JewelsAndStone();
  String J = "aA";
  String S = "aaAbbbb";
  int expected = 3;

  // When
  int result = jewelAndStones.findJewelsInStones(J, S);

  // Then 
  assertEquals(expected, result);
}

In this case, you do not need to do a static import of methods.

In addition to this, you also may use a data-driven approach. Since the leetcode validator use test cases to verify your methods, you can rely on these test-cases as well. Here is a small example of a parameterized test with hamcrest matchers:

import org.junit.Test;
import org.junit.runner.RunWith;
import org.junit.runners.Parameterized;

import java.util.Arrays;
import java.util.Collection;

import static org.hamcrest.CoreMatchers.equalTo;
import static org.hamcrest.CoreMatchers.is;
import static org.junit.Assert.assertThat;

@RunWith(Parameterized.class)
public class JewelsAndStonesTest {
    private String J;
    private String S;
    private int expected;

    public JewelsAndStonesTest(String J, String S, int expected) {
        this.J = J;
        this.S = S;
        this.expected = expected;
    }

    @Parameterized.Parameters(name = "{index}: J=\"{0}\", S=\"{1}\", expected result: {2}")
    public static Collection<Object[]> testCases() {
        return Arrays.asList(new Object[][] {
            {"aA", "aaAbbb", 3}, 
            {"z", "ZZ", 0}
            // add more test cases here: positive and negative 
        });
    }

    @Test
    public void jewelsAndStonesTestSuite() {
       // Given
       JewelsAndStones jewelAndStones = new JewelsAndStone();

       // When 
       int result = jewelAndStones.findJewelsInStones(J, S);

       // Then
       assertThat(result, is(equalTo(expected)));
    }
}