builtins

vm/vm_test.go

@@ -106,6 +106,16 @@ func testExpectedObject(t *testing.T, expected interface{}, actual object.Object
 		if actual != Null {
 			t.Errorf("object is not Null: %T (%+v)", actual, actual)
 		}
+
+	case *object.Error:
+		errObj, ok := actual.(*object.Error)
+		if !ok {
+			t.Errorf("object is not Error: %T (%+v)", actual, actual)
+			return
+		}
+		if errObj.Message != expected.Message {
+			t.Errorf("wrong error message. expected=%q, got=%q", expected.Message, errObj.Message)
+		}
 	}
 }
 
@@ -555,3 +565,49 @@ func TestCallingFunctionsWithWrongArguments(t *testing.T) {
 		}
 	}
 }
+
+func TestBuiltinFunctions(t *testing.T) {
+	tests := []vmTestCase{
+		{`len("")`, 0},
+		{`len("four")`, 4},
+		{`len("hello world")`, 11},
+		{
+			`len(1)`,
+			&object.Error{
+				Message: "argument to `len` not supported, got INTEGER",
+			},
+		},
+		{`len("one", "two")`,
+			&object.Error{
+				Message: "wrong number of arguments. got=2, want=1",
+			},
+		},
+		{`len([1, 2, 3])`, 3},
+		{`len([])`, 0},
+		{`puts("hello", "world!")`, Null},
+		{`first([1, 2, 3])`, 1},
+		{`first([])`, Null},
+		{`first(1)`,
+			&object.Error{
+				Message: "argument to `first` must be ARRAY, got INTEGER",
+			},
+		},
+		{`last([1, 2, 3])`, 3},
+		{`last([])`, Null},
+		{`last(1)`,
+			&object.Error{
+				Message: "argument to `last` must be ARRAY, got INTEGER",
+			},
+		},
+		{`rest([1, 2, 3])`, []int{2, 3}},
+		{`rest([])`, Null},
+		{`push([], 1)`, []int{1}},
+		{`push(1, 1)`,
+			&object.Error{
+				Message: "argument to `push` must be ARRAY, got INTEGER",
+			},
+		},
+	}
+
+	runVmTests(t, tests)
+}