Kotest Konform Matchers

Kotest provides various matchers that can be used with Konform. These matchers can be used in tests to check whether a specified object passes or fails validation.

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

Start with a basic data class:

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

Then given the following user profile validator:

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

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

You can test whether an instance passes validation like this:

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

And you can test whether an instance fails 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'")
}

References

• Konform Matchers | Kotest