Konform Matchers

Kotest provides various matchers for use with Konform. They can be used in your tests to assert that a given object is validated or fails validation.

To use these matchers add implementation 'io.kotest.extensions:kotest-assertions-konform:<version>' to your build. This module is available for both JVM and JS targets.

Let's start with a basic data class:

data class UserProfile(
   val fullName: String,
   val age: Int?
)

Then given a UserProfile validator like this:

val validateUser = Validation<UserProfile> {
  UserProfile::fullName {
     minLength(4)
     maxLength(100)
  }

  UserProfile::age ifPresent {
     minimum(21)
     maximum(99)
  }
}

We can test that instances pass validation like this:

val alice = UserProfile("Alice", 25)
validateUser shouldBeValid user1

And we can test that instances fail validation with specific error messages like this:

val bob = UserProfile("bob", 18)
validateUser.shouldBeInvalid(bob) {
  it.shouldContainError(UserProfile::fullName, "must have at least 4 characters")
  it.shouldContainError(UserProfile::age, "must be at least '21'")
}

Matcher	Description
validation.shouldBeValid(value)	Asserts that the validation is valid for the given value
validation.shouldBeInvalid(value)	Asserts that the validation is invalid for the given value
validation.shouldBeInvalid(value) { block }	Asserts that the validation is invalid for the given value, and then, runs the block with invalid value