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104 lines
2.6 KiB
Go
104 lines
2.6 KiB
Go
// Copyright (c) 2023 - 2025 IBM Corp.
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// All rights reserved.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package testing provides utilities for testing Either monad laws.
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// This is useful for verifying that custom Either implementations satisfy the monad laws.
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package testing
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import (
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"testing"
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ET "github.com/IBM/fp-go/v2/either"
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EQ "github.com/IBM/fp-go/v2/eq"
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L "github.com/IBM/fp-go/v2/internal/monad/testing"
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)
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// AssertLaws asserts that the Either monad satisfies the monad laws.
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// This includes testing:
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// - Identity laws (left and right identity)
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// - Associativity law
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// - Functor laws
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// - Applicative laws
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//
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// Parameters:
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// - t: Testing context
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// - eqe, eqa, eqb, eqc: Equality predicates for the types
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// - ab: Function from A to B for testing
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// - bc: Function from B to C for testing
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//
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// Returns a function that takes a value of type A and returns true if all laws hold.
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//
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// Example:
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//
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// func TestEitherLaws(t *testing.T) {
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// eqInt := eq.FromStrictEquals[int]()
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// eqString := eq.FromStrictEquals[string]()
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// eqError := eq.FromStrictEquals[error]()
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//
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// ab := strconv.Itoa
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// bc := func(s string) bool { return len(s) > 0 }
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//
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// testing.AssertLaws(t, eqError, eqInt, eqString, eq.FromStrictEquals[bool](), ab, bc)(42)
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// }
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func AssertLaws[E, A, B, C any](t *testing.T,
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eqe EQ.Eq[E],
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eqa EQ.Eq[A],
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eqb EQ.Eq[B],
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eqc EQ.Eq[C],
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ab func(A) B,
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bc func(B) C,
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) func(a A) bool {
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return L.AssertLaws(t,
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ET.Eq(eqe, eqa),
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ET.Eq(eqe, eqb),
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ET.Eq(eqe, eqc),
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ET.Of[E, A],
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ET.Of[E, B],
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ET.Of[E, C],
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ET.Of[E, func(A) A],
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ET.Of[E, func(A) B],
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ET.Of[E, func(B) C],
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ET.Of[E, func(func(A) B) B],
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ET.MonadMap[E, A, A],
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ET.MonadMap[E, A, B],
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ET.MonadMap[E, A, C],
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ET.MonadMap[E, B, C],
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ET.MonadMap[E, func(B) C, func(func(A) B) func(A) C],
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ET.MonadChain[E, A, A],
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ET.MonadChain[E, A, B],
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ET.MonadChain[E, A, C],
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ET.MonadChain[E, B, C],
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ET.MonadAp[A, E, A],
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ET.MonadAp[B, E, A],
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ET.MonadAp[C, E, B],
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ET.MonadAp[C, E, A],
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ET.MonadAp[B, E, func(A) B],
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ET.MonadAp[func(A) C, E, func(A) B],
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ab,
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bc,
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)
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}
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