Add test to ensure key/values interp order

Test that interpolated values are returned in the order of the sorted
keys.

config/interpolate_funcs_test.go

@@ -890,6 +890,57 @@ func TestInterpolateFuncKeys(t *testing.T) {
 	})
 }
 
+// Confirm that keys return in sorted order, and values return in the order of
+// their sorted keys.
+func TestInterpolateFuncKeyValOrder(t *testing.T) {
+	testFunction(t, testFunctionConfig{
+		Vars: map[string]ast.Variable{
+			"var.foo": ast.Variable{
+				Type: ast.TypeMap,
+				Value: map[string]ast.Variable{
+					"D": ast.Variable{
+						Value: "2",
+						Type:  ast.TypeString,
+					},
+					"C": ast.Variable{
+						Value: "Y",
+						Type:  ast.TypeString,
+					},
+					"A": ast.Variable{
+						Value: "X",
+						Type:  ast.TypeString,
+					},
+					"10": ast.Variable{
+						Value: "Z",
+						Type:  ast.TypeString,
+					},
+					"1": ast.Variable{
+						Value: "4",
+						Type:  ast.TypeString,
+					},
+					"3": ast.Variable{
+						Value: "W",
+						Type:  ast.TypeString,
+					},
+				},
+			},
+		},
+		Cases: []testFunctionCase{
+			{
+				`${keys(var.foo)}`,
+				[]interface{}{"1", "10", "3", "A", "C", "D"},
+				false,
+			},
+
+			{
+				`${values(var.foo)}`,
+				[]interface{}{"4", "Z", "W", "X", "Y", "2"},
+				false,
+			},
+		},
+	})
+}
+
 func TestInterpolateFuncValues(t *testing.T) {
 	testFunction(t, testFunctionConfig{
 		Vars: map[string]ast.Variable{