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27 lines
837 B
27 lines
837 B
package green.thisfieldwas.embracingnondeterminism.stdlib
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import org.scalatest.matchers.must.Matchers
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import org.scalatest.propspec.AnyPropSpec
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import org.scalatestplus.scalacheck.ScalaCheckPropertyChecks
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import org.scalacheck.Arbitrary.arbitrary
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/** Proves that Scala's List is a functor by definition.
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*/
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class ListSpec extends AnyPropSpec with ScalaCheckPropertyChecks with Matchers {
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property("List.map() preserves identity functions") {
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forAll(arbitrary[List[Int]]) { fa =>
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fa.map(identity) mustBe identity(fa)
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}
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}
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property("List.map() preserves function composition") {
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forAll(for {
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fa <- arbitrary[List[Double]]
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f <- arbitrary[Double => String]
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g <- arbitrary[String => Int]
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} yield (fa, f, g)) { case (fa, f, g) =>
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fa.map(g compose f) mustBe fa.map(f).map(g)
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}
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}
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}
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