fix: refactory tests a bit

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

pair/eq.go

@@ -0,0 +1,33 @@
+// Copyright (c) 2024 IBM Corp.
+// All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package pair
+
+import (
+	EQ "github.com/IBM/fp-go/eq"
+)
+
+// Constructs an equal predicate for an `Either`
+func Eq[A, B any](a EQ.Eq[A], b EQ.Eq[B]) EQ.Eq[Pair[A, B]] {
+	return EQ.FromEquals(func(l, r Pair[A, B]) bool {
+		return a.Equals(Head(l), Head(r)) && b.Equals(Tail(l), Tail(r))
+	})
+
+}
+
+// FromStrictEquals constructs an [EQ.Eq] from the canonical comparison function
+func FromStrictEquals[A, B comparable]() EQ.Eq[Pair[A, B]] {
+	return Eq(EQ.FromStrictEquals[A](), EQ.FromStrictEquals[B]())
+}