import org.junit.*;
import static org.junit.Assert.*;

public class UnitTest {

  @Test
  public void vowelReplace_oneLetterVowelOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("a"));
  }

}

import org.junit.*;
import static org.junit.Assert.*;

public class UnitTest {

  @Test
  public void vowelReplace_oneSOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("a"));
  }

  @Test
  public void vowelReplace_oneEOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("e"));
  }

  @Test
  public void vowelReplace_oneIOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("i"));
  }

  @Test
  public void vowelReplace_oneOOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("o"));
  }

  @Test
  public void vowelReplace_oneUOutputsOneDash_dash() {
    App testApp = new App();
    assertEquals("-", testApp.vowelReplace("u"));
  }

}

add UnitTests for all individual vowels to be replaced by dash (a,e,i,o,u entered one at a time with nothing else)