s2: Add some CellUnion construction test helpers.

Signed-off-by: David Symonds <dsymonds@golang.org>

Author: rsned

s2/s2_test.go

@@ -129,6 +129,15 @@ func randomCellID() CellID {
 	return randomCellIDForLevel(randomUniformInt(maxLevel + 1))
 }
 
+// randomCellUnion returns a CellUnion of the given size of randomly selected cells.
+func randomCellUnion(n int) CellUnion {
+	var cu CellUnion
+	for i := 0; i < n; i++ {
+		cu = append(cu, randomCellID())
+	}
+	return cu
+}
+
 // concentricLoopsPolygon constructs a polygon with the specified center as a
 // number of concentric loops and vertices per loop.
 func concentricLoopsPolygon(center Point, numLoops, verticesPerLoop int) *Polygon {

s2/textformat_test.go

@@ -143,6 +143,16 @@ func makeRect(s string) Rect {
 	return rect
 }
 
+// makeCellUnion returns a CellUnion from the given CellID token strings.
+func makeCellUnion(tokens ...string) CellUnion {
+	var cu CellUnion
+
+	for _, t := range tokens {
+		cu = append(cu, cellIDFromString(t))
+	}
+	return cu
+}
+
 // makeLoop constructs a Loop from the input string.
 // The strings "empty" or "full" create an empty or full loop respectively.
 func makeLoop(s string) *Loop {

s2/textformat_test_test.go

@@ -313,6 +313,42 @@ func TestTextFormatParseRect(t *testing.T) {
 	}
 }
 
+func TestTextFormatMakeCellUnion(t *testing.T) {
+	tests := []struct {
+		have []string
+		want CellUnion
+	}{
+		{
+			have: nil,
+			want: CellUnion{},
+		},
+		{
+			have: []string{},
+			want: CellUnion{},
+		},
+		{
+			have: []string{"google"},
+			want: CellUnion{0},
+		},
+		{
+			have: []string{"0/"},
+			want: CellUnion{CellIDFromFace(0)},
+		},
+		{
+			have: []string{"2/010", "2/011", "2/02"},
+			want: CellUnion{0x4240000000000000, 0x42c0000000000000, 0x4500000000000000},
+		},
+	}
+
+	for _, test := range tests {
+		got := makeCellUnion(test.have...)
+		got.Normalize()
+		if !got.Equal(test.want) {
+			t.Errorf("makeCellUnion(%v) = %v, want %v", test.have, got, test.want)
+		}
+	}
+}
+
 func TestTextFormatMakeLaxPolyline(t *testing.T) {
 	l := makeLaxPolyline("-20:150, -20:151, -19:150")