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More Either tests #2398

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merged 6 commits into from
May 12, 2021
Merged

More Either tests #2398

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b0cd9c4
Simplest tests possible.
a-ivanov May 9, 2021
078accf
Fold and friends tests.
a-ivanov May 10, 2021
dda094a
Remove "condition always true" compiler warning.
a-ivanov May 10, 2021
ea6c4d3
More tests.
a-ivanov May 10, 2021
d92e437
More tests.
a-ivanov May 10, 2021
00f3169
Merge branch 'main' into more-either-tests
rachelcarmena May 12, 2021
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162 changes: 151 additions & 11 deletions arrow-libs/core/arrow-core/src/test/kotlin/arrow/core/EitherTest.kt
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Original file line number Diff line number Diff line change
@@ -1,10 +1,10 @@
package arrow.core

import arrow.core.Either.Left
import arrow.core.Either.Right
import arrow.core.computations.EitherEffect
import arrow.core.computations.RestrictedEitherEffect
import arrow.core.computations.either
import arrow.core.Either.Right
import arrow.core.Either.Left
import arrow.core.test.UnitSpec
import arrow.core.test.generators.any
import arrow.core.test.generators.either
Expand All @@ -18,6 +18,7 @@ import arrow.core.test.laws.FxLaws
import arrow.core.test.laws.MonoidLaws
import arrow.typeclasses.Monoid
import io.kotlintest.properties.Gen
import io.kotlintest.properties.PropertyContext
import io.kotlintest.properties.forAll
import io.kotlintest.shouldBe
import io.kotlintest.shouldThrow
Expand All @@ -38,6 +39,61 @@ class EitherTest : UnitSpec() {
}
)

"isLeft should return true if Left and false if Right" {
forAll { a: Int ->
Left(a).isLeft() && !Right(a).isLeft()
}
}

"isRight should return false if Left and true if Right" {
forAll { a: Int ->
!Left(a).isRight() && Right(a).isRight()
}
}

"fold should apply first op if Left and second op if Right" {
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.fold({ it + 2 }, { it + 1 }) == a + 1 &&
left.fold({ it + 2 }, { it + 1 }) == b + 2
}
}

"foldLeft should return initial if Left and apply op if Right" {
forAllSmallInt { a: Int, b: Int, c: Int ->
Right(a).foldLeft(c, Int::plus) == c + a &&
Left(b).foldLeft(c, Int::plus) == c
}
}

"foldMap should return the empty of the inner type if Left and apply op if Right" {
forAllSmallInt { a: Int, b: Int ->
val left: Either<Int, Int> = Left(b)

Right(a).foldMap(Monoid.int()) { it + 1 } == a + 1 &&
left.foldMap(Monoid.int()) { it + 1 } == Monoid.int().empty()
}
}

"bifoldLeft should apply first op if Left and apply second op if Right" {
forAllSmallInt { a: Int, b: Int, c: Int ->
Right(a).bifoldLeft(c, Int::plus, Int::times) == a * c &&
Left(b).bifoldLeft(c, Int::plus, Int::times) == b + c
}
}

"bifoldMap should apply first op if Left and apply second op if Right" {
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.bifoldMap(Monoid.int(), { it + 2 }, { it + 1 }) == a + 1 &&
left.bifoldMap(Monoid.int(), { it + 2 }, { it + 1 }) == b + 2
}
}

"fromNullable should lift value as a Right if it is not null" {
forAll { a: Int ->
Either.fromNullable(a) == Right(a)
Expand All @@ -49,9 +105,7 @@ class EitherTest : UnitSpec() {
}

"empty should return a Right of the empty of the inner type" {
forAll { _: String ->
Right(Monoid.string().empty()) == Monoid.either(Monoid.string(), Monoid.string()).empty()
}
Right(Monoid.string().empty()) shouldBe Monoid.either(Monoid.string(), Monoid.string()).empty()
}

"combine two rights should return a right of the combine of the inners" {
Expand Down Expand Up @@ -82,7 +136,7 @@ class EitherTest : UnitSpec() {

"orNull should return value" {
forAll { a: Int ->
Either.Right(a).orNull() == a
Right(a).orNull() == a
}
}

Expand All @@ -94,7 +148,7 @@ class EitherTest : UnitSpec() {
}

"filterOrElse should filter values" {
forAll(Gen.intSmall(), Gen.intSmall()) { a: Int, b: Int ->
forAllSmallInt { a: Int, b: Int ->
val left: Either<Int, Int> = Left(a)

Right(a).filterOrElse({ it > a - 1 }, { b }) == Right(a) &&
Expand All @@ -105,7 +159,7 @@ class EitherTest : UnitSpec() {
}

"filterOrOther should filter values" {
forAll(Gen.intSmall(), Gen.intSmall()) { a: Int, b: Int ->
forAllSmallInt { a: Int, b: Int ->
val left: Either<Int, Int> = Left(a)

Right(a).filterOrOther({ it > a - 1 }, { b + a }) == Right(a) &&
Expand All @@ -123,6 +177,17 @@ class EitherTest : UnitSpec() {
}
}

"exists should apply predicate to Right only" {
forAllSmallInt { a: Int ->
val left: Either<Int, Int> = Left(a)

Right(a).exists { it > a - 1 } &&
!Right(a).exists { it > a + 1 } &&
!left.exists { it > a - 1 } &&
!left.exists { it > a + 1 }
}
}

"rightIfNotNull should return Left if value is null or Right of value when not null" {
forAll { a: Int, b: Int ->
null.rightIfNotNull { b } == Left(b) &&
Expand All @@ -146,13 +211,15 @@ class EitherTest : UnitSpec() {

"orNull should convert" {
forAll { a: Int ->
val left: Either<Int, Int> = Left(a)

Right(a).orNull() == a &&
Left(a).orNull() == null
left.orNull() == null
}
}

"contains should check value" {
forAll(Gen.intSmall(), Gen.intSmall()) { a: Int, b: Int ->
forAllSmallInt { a: Int, b: Int ->
val rightContains = Right(a).contains(a)
// We need to check that a != b or this test will result in a false negative
val rightDoesntContains = if (a != b) !Right(a).contains(b) else true
Expand All @@ -162,14 +229,78 @@ class EitherTest : UnitSpec() {
}
}

"map should alter right instance only" {
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.map { it + 1 } == Right(a + 1) && left.map { it + 1 } == left
}
}

"mapLeft should alter left instance only" {
forAll(Gen.intSmall(), Gen.intSmall()) { a: Int, b: Int ->
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.mapLeft { it + 1 } == right && left.mapLeft { it + 1 } == Left(b + 1)
}
}

"bimap should alter left or right instance accordingly" {
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.bimap({ it + 2 }, { it + 1 }) == Right(a + 1) &&
left.bimap({ it + 2 }, { it + 1 }) == Left(b + 2)
}
}

"replicate should return Right(empty list) when n <= 0" {
forAll(
Gen.oneOf(Gen.negativeIntegers(), Gen.constant(0)),
Gen.int()
) { n: Int, a: Int ->
val expected: Either<Int, List<Int>> = Right(emptyList())

Right(a).replicate(n) == expected &&
Left(a).replicate(n) == expected
}
}

"replicate should return Right(list of repeated value size n) when Right and n is positive" {
forAll(
Gen.intSmall().filter { it > 0 },
Gen.int()
) { n: Int, a: Int ->
Right(a).replicate(n) == Right(List(n) { a }) &&
Left(a).replicate(n) == Left(a)
}
}

"traverse should return list of Right when Right and empty list when Left" {
forAll(
Gen.int(),
Gen.int(),
Gen.int()
) { a: Int, b: Int, c: Int ->
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@a-ivanov a-ivanov May 10, 2021 •
edited
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Gen.list is also possible, but I thought that showing list of Right is more explicit.

Right(a).traverse { emptyList<Int>() } == emptyList<Int>() &&
Right(a).traverse { listOf(b, c) } == listOf(Right(b), Right(c)) &&
Left(a).traverse { listOf(b, c) } == emptyList<Int>()
}
}

"flatMap should map right instance only" {
forAllSmallInt { a: Int, b: Int ->
val right: Either<Int, Int> = Right(a)
val left: Either<Int, Int> = Left(b)

right.flatMap { Right(it + 1) } == Right(a + 1) &&
left.flatMap { Right(it + 1) } == left
}
}

"conditionally should create right instance only if test is true" {
forAll { t: Boolean, i: Int, s: String ->
val expected = if (t) Right(i) else Left(s)
Expand Down Expand Up @@ -323,3 +454,12 @@ private suspend fun <A> throwException(
a: A
): Either<Throwable, Any> =
throw RuntimeException("An Exception is thrown while handling the result of the supplied function.")

private fun forAllSmallInt(fn: PropertyContext.(a: Int) -> Boolean) =
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I believe we have some other utilities like these somewhere. Perhaps these functions should be moved there and made public or internal.

forAll(Gen.intSmall(), fn)

private fun forAllSmallInt(fn: PropertyContext.(a: Int, b: Int) -> Boolean) =
forAll(Gen.intSmall(), Gen.intSmall(), fn)

private fun forAllSmallInt(fn: PropertyContext.(a: Int, b: Int, c: Int) -> Boolean) =
forAll(Gen.intSmall(), Gen.intSmall(), Gen.intSmall(), fn)