fix: add ioeither

Signed-off-by: Dr. Carsten Leue <carsten.leue@de.ibm.com>

ioeither/testing/laws.go

@@ -0,0 +1,61 @@
+package testing
+
+import (
+	"testing"
+
+	ET "github.com/ibm/fp-go/either"
+	EQ "github.com/ibm/fp-go/eq"
+	L "github.com/ibm/fp-go/internal/monad/testing"
+	IOE "github.com/ibm/fp-go/ioeither"
+)
+
+// AssertLaws asserts the apply monad laws for the `IOEither` monad
+func AssertLaws[E, A, B, C any](t *testing.T,
+	eqe EQ.Eq[E],
+	eqa EQ.Eq[A],
+	eqb EQ.Eq[B],
+	eqc EQ.Eq[C],
+
+	ab func(A) B,
+	bc func(B) C,
+) func(a A) bool {
+
+	return L.AssertLaws(t,
+		IOE.Eq(ET.Eq(eqe, eqa)),
+		IOE.Eq(ET.Eq(eqe, eqb)),
+		IOE.Eq(ET.Eq(eqe, eqc)),
+
+		IOE.Of[E, A],
+		IOE.Of[E, B],
+		IOE.Of[E, C],
+
+		IOE.Of[E, func(A) A],
+		IOE.Of[E, func(A) B],
+		IOE.Of[E, func(B) C],
+		IOE.Of[E, func(func(A) B) B],
+
+		IOE.MonadMap[E, A, A],
+		IOE.MonadMap[E, A, B],
+		IOE.MonadMap[E, A, C],
+		IOE.MonadMap[E, B, C],
+
+		IOE.MonadMap[E, func(B) C, func(func(A) B) func(A) C],
+
+		IOE.MonadChain[E, A, A],
+		IOE.MonadChain[E, A, B],
+		IOE.MonadChain[E, A, C],
+		IOE.MonadChain[E, B, C],
+
+		IOE.MonadAp[A, E, A],
+		IOE.MonadAp[B, E, A],
+		IOE.MonadAp[C, E, B],
+		IOE.MonadAp[C, E, A],
+
+		IOE.MonadAp[B, E, func(A) B],
+		IOE.MonadAp[func(A) C, E, func(A) B],
+
+		ab,
+		bc,
+	)
+
+}

ioeither/testing/laws_test.go

@@ -0,0 +1,33 @@
+package testing
+
+import (
+	"fmt"
+	"testing"
+
+	EQ "github.com/ibm/fp-go/eq"
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMonadLaws(t *testing.T) {
+	// some comparison
+	eqe := EQ.FromStrictEquals[string]()
+	eqa := EQ.FromStrictEquals[bool]()
+	eqb := EQ.FromStrictEquals[int]()
+	eqc := EQ.FromStrictEquals[string]()
+
+	ab := func(a bool) int {
+		if a {
+			return 1
+		}
+		return 0
+	}
+
+	bc := func(b int) string {
+		return fmt.Sprintf("value %d", b)
+	}
+
+	laws := AssertLaws(t, eqe, eqa, eqb, eqc, ab, bc)
+
+	assert.True(t, laws(true))
+	assert.True(t, laws(false))
+}