proposal: Add OneOf Matcher

gomock/matchers.go

@@ -219,6 +219,27 @@ func (m lenMatcher) String() string {
 	return fmt.Sprintf("has length %d", m.i)
 }
 
+type oneOfMatcher struct {
+	matches []interface{}
+}
+
+func oneOf(matches []interface{}) Matcher {
+	return oneOfMatcher{matches: matches}
+}
+
+func (m oneOfMatcher) Matches(x interface{}) bool {
+	for _, u := range m.matches {
+		if u == x {
+			return true
+		}
+	}
+	return false
+}
+
+func (m oneOfMatcher) String() string {
+	return fmt.Sprintf("is one of %+v", m.matches)
+}
+
 type inAnyOrderMatcher struct {
 	x any
 }
@@ -366,3 +387,14 @@ func AssignableToTypeOf(x any) Matcher {
 func InAnyOrder(x any) Matcher {
 	return inAnyOrderMatcher{x}
 }
+
+// OneOf is a Matcher that returns true when the parameter of the mock is
+// part of the set provided to the matcher
+//
+// Example Usage:
+//
+//	OneOf([]any{100,200,300})
+//	OneOf([]any{"Go", "Gopher"})
+func OneOf(x []any) Matcher {
+	return oneOfMatcher{x}
+}

gomock/matchers_test.go

@@ -54,6 +54,7 @@ func TestMatchers(t *testing.T) {
 			[]e{[]string{"a"}, A{"b"}},
 		},
 		{"test Cond", gomock.Cond(func(x any) bool { return x.(B).Name == "Dam" }), []e{B{Name: "Dam"}}, []e{B{Name: "Dave"}}},
+		{"test OneOf", gomock.OneOf([]any{1, 2, 3}), []e{1, 2, 3}, []e{4, 5, 6}},
 	}
 	for _, tt := range tests {
 		t.Run(tt.name, func(t *testing.T) {
@@ -145,6 +146,54 @@ func TestAssignableToTypeOfMatcher(t *testing.T) {
 	}
 }
 
+func TestOneOf(t *testing.T) {
+	tests := []struct {
+		name      string
+		wanted    []any
+		given     any
+		wantMatch bool
+	}{
+		{
+			name:      "match for one of many",
+			wanted:    []any{1, 2, 3},
+			given:     1,
+			wantMatch: true,
+		},
+		{
+			name:      "match for single",
+			wanted:    []any{1},
+			given:     1,
+			wantMatch: true,
+		},
+		{
+			name:      "match for mixed types",
+			wanted:    []any{1, "5", 0x4},
+			given:     0x4,
+			wantMatch: true,
+		},
+		{
+			name:      "not match for empty slice",
+			wanted:    []any{},
+			given:     1,
+			wantMatch: false,
+		},
+		{
+			name:      "not match for type mismatch",
+			wanted:    []any{1, 2, 3},
+			given:     "a",
+			wantMatch: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			if got := gomock.OneOf(tt.wanted).Matches(tt.given); got != tt.wantMatch {
+				t.Errorf("got = %v, wantMatch %v", got, tt.wantMatch)
+			}
+		})
+	}
+}
+
 func TestInAnyOrder(t *testing.T) {
 	tests := []struct {
 		name      string