1 files changed, 205 insertions, 0 deletions
diff --git a/src/go/types/typeterm_test.go b/src/go/types/typeterm_test.go
new file mode 100644
index 0000000000..391ff3e05f
--- /dev/null
+++ b/src/go/types/typeterm_test.go
@@ -0,0 +1,205 @@
+// Copyright 2021 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package types
+
+import (
+	"strings"
+	"testing"
+)
+
+var testTerms = map[string]*term{
+	"∅":       nil,
+	"⊤":       {},
+	"int":     {false, Typ[Int]},
+	"~int":    {true, Typ[Int]},
+	"string":  {false, Typ[String]},
+	"~string": {true, Typ[String]},
+	// TODO(gri) add a defined type
+}
+
+func TestTermString(t *testing.T) {
+	for want, x := range testTerms {
+		if got := x.String(); got != want {
+			t.Errorf("%v.String() == %v; want %v", x, got, want)
+		}
+	}
+}
+
+func split(s string, n int) []string {
+	r := strings.Split(s, " ")
+	if len(r) != n {
+		panic("invalid test case: " + s)
+	}
+	return r
+}
+
+func testTerm(name string) *term {
+	r, ok := testTerms[name]
+	if !ok {
+		panic("invalid test argument: " + name)
+	}
+	return r
+}
+
+func TestTermEqual(t *testing.T) {
+	for _, test := range []string{
+		"∅ ∅ T",
+		"⊤ ⊤ T",
+		"int int T",
+		"~int ~int T",
+		"∅ ⊤ F",
+		"∅ int F",
+		"∅ ~int F",
+		"⊤ int F",
+		"⊤ ~int F",
+		"int ~int F",
+	} {
+		args := split(test, 3)
+		x := testTerm(args[0])
+		y := testTerm(args[1])
+		want := args[2] == "T"
+		if got := x.equal(y); got != want {
+			t.Errorf("%v.equal(%v) = %v; want %v", x, y, got, want)
+		}
+		// equal is symmetric
+		x, y = y, x
+		if got := x.equal(y); got != want {
+			t.Errorf("%v.equal(%v) = %v; want %v", x, y, got, want)
+		}
+	}
+}
+
+func TestTermUnion(t *testing.T) {
+	for _, test := range []string{
+		"∅ ∅ ∅ ∅",
+		"∅ ⊤ ⊤ ∅",
+		"∅ int int ∅",
+		"∅ ~int ~int ∅",
+		"⊤ ⊤ ⊤ ∅",
+		"⊤ int ⊤ ∅",
+		"⊤ ~int ⊤ ∅",
+		"int int int ∅",
+		"int ~int ~int ∅",
+		"int string int string",
+		"int ~string int ~string",
+		"~int ~string ~int ~string",
+
+		// union is symmetric, but the result order isn't - repeat symmetric cases explictly
+		"⊤ ∅ ⊤ ∅",
+		"int ∅ int ∅",
+		"~int ∅ ~int ∅",
+		"int ⊤ ⊤ ∅",
+		"~int ⊤ ⊤ ∅",
+		"~int int ~int ∅",
+		"string int string int",
+		"~string int ~string int",
+		"~string ~int ~string ~int",
+	} {
+		args := split(test, 4)
+		x := testTerm(args[0])
+		y := testTerm(args[1])
+		want1 := testTerm(args[2])
+		want2 := testTerm(args[3])
+		if got1, got2 := x.union(y); !got1.equal(want1) || !got2.equal(want2) {
+			t.Errorf("%v.union(%v) = %v, %v; want %v, %v", x, y, got1, got2, want1, want2)
+		}
+	}
+}
+
+func TestTermIntersection(t *testing.T) {
+	for _, test := range []string{
+		"∅ ∅ ∅",
+		"∅ ⊤ ∅",
+		"∅ int ∅",
+		"∅ ~int ∅",
+		"⊤ ⊤ ⊤",
+		"⊤ int int",
+		"⊤ ~int ~int",
+		"int int int",
+		"int ~int int",
+		"int string ∅",
+		"int ~string ∅",
+		"~int ~string ∅",
+	} {
+		args := split(test, 3)
+		x := testTerm(args[0])
+		y := testTerm(args[1])
+		want := testTerm(args[2])
+		if got := x.intersect(y); !got.equal(want) {
+			t.Errorf("%v.intersect(%v) = %v; want %v", x, y, got, want)
+		}
+		// intersect is symmetric
+		x, y = y, x
+		if got := x.intersect(y); !got.equal(want) {
+			t.Errorf("%v.intersect(%v) = %v; want %v", x, y, got, want)
+		}
+	}
+}
+
+func TestTermIncludes(t *testing.T) {
+	for _, test := range []string{
+		"∅ int F",
+		"⊤ int T",
+		"int int T",
+		"~int int T",
+		"string int F",
+		"~string int F",
+	} {
+		args := split(test, 3)
+		x := testTerm(args[0])
+		y := testTerm(args[1]).typ
+		want := args[2] == "T"
+		if got := x.includes(y); got != want {
+			t.Errorf("%v.includes(%v) = %v; want %v", x, y, got, want)
+		}
+	}
+}
+
+func TestTermSubsetOf(t *testing.T) {
+	for _, test := range []string{
+		"∅ ∅ T",
+		"⊤ ⊤ T",
+		"int int T",
+		"~int ~int T",
+		"∅ ⊤ T",
+		"∅ int T",
+		"∅ ~int T",
+		"⊤ int F",
+		"⊤ ~int F",
+		"int ~int T",
+	} {
+		args := split(test, 3)
+		x := testTerm(args[0])
+		y := testTerm(args[1])
+		want := args[2] == "T"
+		if got := x.subsetOf(y); got != want {
+			t.Errorf("%v.subsetOf(%v) = %v; want %v", x, y, got, want)
+		}
+	}
+}
+
+func TestTermDisjoint(t *testing.T) {
+	for _, test := range []string{
+		"int int F",
+		"~int ~int F",
+		"int ~int F",
+		"int string T",
+		"int ~string T",
+		"~int ~string T",
+	} {
+		args := split(test, 3)
+		x := testTerm(args[0])
+		y := testTerm(args[1])
+		want := args[2] == "T"
+		if got := x.disjoint(y); got != want {
+			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
+		}
+		// disjoint is symmetric
+		x, y = y, x
+		if got := x.disjoint(y); got != want {
+			t.Errorf("%v.disjoint(%v) = %v; want %v", x, y, got, want)
+		}
+	}
+}