Unit test Example

PasswordTest.kt

class PasswordTest{
  
  @Test
  fun `validatePassword blank input expected required field`(){
    val sut = Utils()
    val result = sut.validatePassword("     ")
    assertEquals("Password is required field", result)
  }
  @Test
  fun `validatePassword 2CharInput expected validation Msg`(){
    val sut = Utils()
    val result = sut.validatePassword("ab")
    assertEquals("Length of the password should be greater than 6",result)
  }
  @Test
  fun `validatePassword correctInput expected valid password`(){
    val sut = Utils()
    val result = sut.validatePassword("Pass123")
    assertEquals("valid",result)
  }
}

StringTest.kt

class StringTest{

  @Test
  fun `testStringReversal Empty String expected Empty String`(){
    val sut = Utils()
    val result = sut.reverseString(input:"")
    assertEquals("",result)
  }
  
   @Test
  fun `testStringReversal Single Char expected Single Char`(){
    val sut = Utils()
    val result = sut.reverseString(input:"a")
    assertEquals("a",result)
  }
  
   @Test
  fun `testStringReversal valid input expected same String`(){
    val sut = Utils()
    val result = sut.reverseString(input:"ArunKumar")
    assertEquals("ramuKnurA",result)
  }
  
   @Test(expected = IllegalArgumentException::class)
  fun `testStringReversal valid input expected same String`(){
    val sut = Utils()
    val result = sut.reverseString(input:null)
  }
}

Utils.kt

class Utils{

  fun validatePassword(input: String) = when {
      input.isBlank() -> {
          "Password is required field"
      }
      input.length < 6 -> {
          "Length of the password should be greater than 6"
      }
      input.length > 15 -> {
          "Length of the password should be less than 15"
      }
      else -> {
          "Valid"
      }
  }
  
  fun reverseString(input: String?):String{
    
    if(input == null){
        throw IllegalArgumentException("Input String is Required")
    }
    var chars = input.toCharArray()
    var i = 0
    var j = chars.size - 1
    
    while(i < j){
        val temp = chars[i]
        chars[i] = chars[j]
        chars[j] = temp
        i++
        j--
    }
    return chars.joinToString(separator: "")
  }
}