Monkey/parser/parser_test.go

package parser

import (
	"fmt"
	"github/runnignwater/monkey/ast"
	"github/runnignwater/monkey/lexer"
	"log"
	"testing"
)

/**
 * @Author: simon
 * @Author: ynwdlxm@163.com
 * @Date: 2022/10/2 下午10:40
 * @Desc: LetStatement test case
 */
func TestLetStatements(t *testing.T) {
	input := `
        let x = 5;
        let y = 10;
        
        let foo = 838383;
        `
	l := lexer.New(input)
	p := New(l)

	program := p.ParseProgram()
	checkParseErrors(t, p)
	if program == nil {
		t.Fatalf("ParseProgram() return nil")
	}
	if len(program.Statements) != 3 {
		t.Fatalf("Program.Statements does not contain 3 statements. got=%d", len(program.Statements))
	}

	tests := []struct {
		expectedIdentifies string
	}{
		{"x"},
		{"y"},
		{"foo"},
	}

	for i, tt := range tests {
		stmt := program.Statements[i]
		if !testLetStatement(t, stmt, tt.expectedIdentifies) {
			return
		}
	}
}

func TestReturnStatements(t *testing.T) {
	input := `
        return 5;
        return 10;
        return add(a,10);
    `
	l := lexer.New(input)
	p := New(l)

	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 3 {
		t.Fatalf("Program.Statements does not contain 3 statements. got=%d", len(program.Statements))
	}

	for _, stmt := range program.Statements {
		returnStmt, ok := stmt.(*ast.ReturnStatement)
		if !ok {
			t.Errorf("stmt not *ast.ReturnStatement. got=%T", stmt)
			continue
		}
		if returnStmt.TokenLiteral() != "return" {
			t.Errorf("returnStmt.TokenLiteral not 'return', got %q", returnStmt.TokenLiteral())
		}
	}
}

func checkParseErrors(t *testing.T, p *Parser) {
	errors := p.errors
	if len(errors) == 0 {
		return
	}
	t.Errorf("parse has %d errors.", len(errors))
	for _, msg := range errors {
		t.Errorf("parse error: %q", msg)
	}
	t.FailNow()
}

func testLetStatement(t *testing.T, s ast.Statement, name string) bool {
	if s.TokenLiteral() != "let" {
		t.Errorf("s.TokenLiteral() not 'let'. got =%q", s.TokenLiteral())
		return false
	}

	letStmt, ok := s.(*ast.LetStatement)
	if !ok {
		t.Errorf("s is not *ast.LetStatement. got=%T", s)
		return false
	}

	if letStmt.Name.Value != name {
		t.Errorf("letStmt.Name.Value not '%s'. got=%s", name, letStmt.Name.Value)
		return false
	}

	if letStmt.Name.TokenLiteral() != name {
		t.Errorf("s.name not '%s. got=%s", name, letStmt.Name)
		return false
	}

	return true
}

func TestIdentifier(t *testing.T) {
	input := "foobar;"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program has not enough statements. got=%d", len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
			program.Statements[0])
	}

	ident, ok := stmt.Expression.(*ast.Identifier)
	if !ok {
		t.Fatalf("exp not *ast.Identifier. got=%T", stmt.Expression)
	}

	if ident.Value != "foobar" {
		t.Fatalf("ident.Value not %s. got=%s", "foobar", ident.Value)
	}
	if ident.TokenLiteral() != "foobar" {
		t.Errorf("ident.TokenLiteral() not %s. got=%s", "foobar", ident.TokenLiteral())
	}
}

func TestIntegerLiteralExpression(t *testing.T) {
	input := "5;"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program has not enough statements. got=%d",
			len(program.Statements))
	}
	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
			program.Statements[0])
	}
	literal, ok := stmt.Expression.(*ast.IntegerLiteral)
	if !ok {
		t.Fatalf("exp not *ast.IntegerLiteral. got=%T", stmt.Expression)
	}
	if literal.Value != 5 {
		t.Errorf("literal.Value not %d. got=%d", 5, literal.Value)
	}
	if literal.TokenLiteral() != "5" {
		t.Errorf("literal.TokenLiteral not %s. got=%s", "5",
			literal.TokenLiteral())
	}
}

/**
*  Prefix Operators or "prefix expressions"
*  <prefix operator><expression>;
*  -5;
*  !foobar;
*  5 + -10;
 */
func TestParsingPrefixExpressions(t *testing.T) {
	prefixTests := []struct {
		input        string
		operator     string
		integerValue int64
	}{
		{"!5;", "!", 5},
		{"-15;", "-", 15},
	}

	for _, tt := range prefixTests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParseErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statement does not contain %d statements. got=%d\n",
				1, len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
				program.Statements[0])
		}
		exp, ok := stmt.Expression.(*ast.PrefixExpression)
		if !ok {
			log.Fatalf("stmt is not ast.PrefixExpression. got=%T", stmt.Expression)
		}
		if exp.Operator != tt.operator {
			t.Fatalf("exp.Operator is not '%s'. got=%s",
				tt.operator, exp.Operator)
		}
		if !testIntegerLiteral(t, exp.Right, tt.integerValue) {
			return
		}
	}
}

func testIntegerLiteral(t *testing.T, il ast.Expression, value int64) bool {
	integ, ok := il.(*ast.IntegerLiteral)
	if !ok {
		t.Errorf("il not *ast.IntegerLiteral. got=%T", il)
		return false
	}
	if integ.Value != value {
		t.Errorf("integ.Value not %d. get=%d", value, integ.Value)
		return false
	}
	if integ.TokenLiteral() != fmt.Sprintf("%d", value) {
		t.Errorf("integ.TokenLiteral not %d. got=%s", value, integ.TokenLiteral())
		return false
	}
	return true
}

func testLiteralExpression(t *testing.T, exp ast.Expression, expected interface{}) bool {
	switch v := expected.(type) {
	case int:
		return testIntegerLiteral(t, exp, int64(v))
	case int64:
		return testIntegerLiteral(t, exp, v)
	case string:
		return testIdentifier(t, exp, v)
	case bool:
		return testBooleanLiteral(t, exp, v)
	}
	t.Errorf("type of exp not hand. got=%T", exp)
	return false
}

func testBooleanLiteral(t *testing.T, exp ast.Expression, value bool) bool {
	bo, ok := exp.(*ast.Boolean)
	if !ok {
		t.Errorf("exp not *ast.Boolean. got=%T", exp)
		return false
	}
	if bo.Value != value {
		t.Errorf("bo.Value not %t. got=%t", value, bo.Value)
		return false
	}
	if bo.TokenLiteral() != fmt.Sprintf("%t", value) {
		t.Errorf("bo.TokenLiteral not %t. got=%s", value, bo.TokenLiteral())
		return false
	}
	return true
}

func testIdentifier(t *testing.T, exp ast.Expression, v string) bool {
	ident, ok := exp.(*ast.Identifier)
	if !ok {
		t.Errorf("exp not *ast.Identifier. got=%T", exp)
		return false
	}
	if ident.Value != v {
		t.Errorf("ident.Value not %s. got=%s", v, ident.Value)
		return false
	}
	if ident.TokenLiteral() != v {
		t.Errorf("ident.TokenLiteral not %s. got=%s", v,
			ident.TokenLiteral())
		return false
	}
	return true
}

// <expression> <infix operator> <expression>
func TestParsingInfixExpressions(t *testing.T) {
	infixTests := []struct {
		input      string
		leftValue  int64
		operator   string
		rightValue int64
	}{
		{"5 + 5", 5, "+", 5},
		{"5 - 5", 5, "-", 5},
		{"5 * 5", 5, "*", 5},
		{"5 / 5", 5, "/", 5},
		{"5 > 5", 5, ">", 5},
		{"5 < 5", 5, "<", 5},
		{"5 == 5", 5, "==", 5},
		{"5 != 5", 5, "!=", 5},
	}

	for _, tt := range infixTests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParseErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program.Statements does not contain %d statements. got=%d\n",
				1, len(program.Statements))
		}
		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
				program.Statements[0])
		}
		exp, ok := stmt.Expression.(*ast.InfixExpression)
		if !ok {
			t.Fatalf("exp is not ast.InfixExpression. got =%T", stmt.Expression)
		}
		if !testIntegerLiteral(t, exp.Left, tt.leftValue) {
			return
		}
		if exp.Operator != tt.operator {
			t.Fatalf("exp.Operator is not '%s'. got=%s", tt.operator, exp.Operator)
		}
		if !testIntegerLiteral(t, exp.Right, tt.rightValue) {
			return
		}
	}
}

// 操作符 优先级测试
func TestOperatorPrecedenceParsing(t *testing.T) {
	tests := []struct {
		input    string
		expected string
	}{
		{
			"-a * b",
			"((-a) * b)",
		},
		{
			"!-a",
			"(!(-a))",
		},
		{
			"a + b + c",
			"((a + b) + c)",
		},
		{
			"a + b - c",
			"((a + b) - c)",
		},
		{
			"a * b * c",
			"((a * b) * c)",
		},
		{
			"a * b / c",
			"((a * b) / c)",
		},
		{
			"a + b / c",
			"(a + (b / c))",
		},
		{
			"a + b * c + d / e - f",
			"(((a + (b * c)) + (d / e)) - f)",
		},
		{
			"3 + 4; -5 *5",
			"(3 + 4)((-5) * 5)",
		},
		{
			"5 > 4 == 3 < 4",
			"((5 > 4) == (3 < 4))",
		},
		{
			"5 < 4 != 3 > 4",
			"((5 < 4) != (3 > 4))",
		},
		{
			"3 + 4 * 5 == 3 * 1 + 4 * 5",
			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
		},
		{
			"3 + 4 * 5 == 3 * 1 + 4 * 5",
			"((3 + (4 * 5)) == ((3 * 1) + (4 * 5)))",
		},
		{
			"3 > 5 == false",
			"((3 > 5) == false)",
		},
		{
			"1 + (2 + 3) + 4",
			"((1 + (2 + 3)) + 4)",
		},
		{
			"(5 + 5) * 2",
			"((5 + 5) * 2)",
		},
		{
			"2 / (5 + 5)",
			"(2 / (5 + 5))"},
		{
			"-(5 + 5)",
			"(-(5 + 5))"},
		{
			"!(true == true)", "(!(true == true))",
		},
		{
			"a * [1, 2, 3, 4][b * c] *d",
			"((a * ([1, 2, 3, 4][(b * c)])) * d)",
		},
		{
			"add(a * b[2], b[1], 2 * [1, 2][1])",
			"add((a * (b[2])), (b[1]), (2 * ([1, 2][1])))",
		},
	}

	for _, tt := range tests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParseErrors(t, p)

		actual := program.String()
		if actual != tt.expected {
			t.Errorf("exptected=%q,\n got=%q", tt.expected, actual)
		}
	}
}

func TestBooleanExpression(t *testing.T) {
	tests := []struct {
		input           string
		expectedBoolean bool
	}{
		{"true;", true},
		{"false;", false},
	}

	for _, tt := range tests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParseErrors(t, p)

		if len(program.Statements) != 1 {
			t.Fatalf("program has not enough statements. got=%d",
				len(program.Statements))
		}

		stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
		if !ok {
			t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
				program.Statements[0])
		}

		boolean, ok := stmt.Expression.(*ast.Boolean)
		if !ok {
			t.Fatalf("exp not *ast.Boolean. got=%T", stmt.Expression)
		}
		if boolean.Value != tt.expectedBoolean {
			t.Errorf("boolean.Value not %t. got=%t", tt.expectedBoolean,
				boolean.Value)
		}
	}
}

func TestIfExpression(t *testing.T) {
	input := `if (x < y) { x }`
	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program.Body does not contain %d statements. got=%d\n",
			1, len(program.Statements))
	}
	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}
	exp, ok := stmt.Expression.(*ast.IfExpression)
	if !ok {
		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
	}

	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
		return
	}
	if len(exp.Consequence.Statements) != 1 {
		t.Errorf("consequence is not 1 statements. got=%d\n",
			len(exp.Consequence.Statements))
	}
	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T", exp.Consequence.Statements[0])
	}
	if !testIdentifier(t, consequence.Expression, "x") {
		return
	}
	if exp.Alternative != nil {
		t.Errorf("exp.Alternative.Statements was not nil. got=%+v", exp.Alternative)
	}
}

func TestIfElseExpression(t *testing.T) {
	input := `if (x < y) { x } else { y }`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program.Body does not contain %d statements. got=%d\n",
			1, len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statements[0] is not ast.ExpressionStatement. got=%T",
			program.Statements[0])
	}

	exp, ok := stmt.Expression.(*ast.IfExpression)
	if !ok {
		t.Fatalf("stmt.Expression is not ast.IfExpression. got=%T", stmt.Expression)
	}

	if !testInfixExpression(t, exp.Condition, "x", "<", "y") {
		return
	}

	if len(exp.Consequence.Statements) != 1 {
		t.Errorf("consequence is not 1 statements. got=%d\n",
			len(exp.Consequence.Statements))
	}

	consequence, ok := exp.Consequence.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
			exp.Consequence.Statements[0])
	}

	if !testIdentifier(t, consequence.Expression, "x") {
		return
	}

	if len(exp.Alternative.Statements) != 1 {
		t.Errorf("exp.Alternative.Statements does not contain 1 statements. got=%d\n",
			len(exp.Alternative.Statements))
	}

	alternative, ok := exp.Alternative.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("Statements[0] is not ast.ExpressionStatement. got=%T",
			exp.Alternative.Statements[0])
	}

	if !testIdentifier(t, alternative.Expression, "y") {
		return
	}
}

func testInfixExpression(t *testing.T, exp ast.Expression, left interface{},
	operator string, right interface{}) bool {

	opExp, ok := exp.(*ast.InfixExpression)
	if !ok {
		t.Errorf("exp is not ast.OperatorExpression. got=%T(%s)", exp, exp)
		return false
	}

	if !testLiteralExpression(t, opExp.Left, left) {
		return false
	}

	if opExp.Operator != operator {
		t.Errorf("exp.Operator is not '%s'. got=%q", operator, opExp.Operator)
		return false
	}

	if !testLiteralExpression(t, opExp.Right, right) {
		return false
	}

	return true
}

func TestFunctionLiteral(t *testing.T) {
	input := `fn(x,y) {x+y}`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("Program.Body does not contain %d statements. got=%d\n", 1, len(program.Statements))
	}
	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("program.Statement[0] is not ast.ExpressionStatemtn. got=%T", program.Statements[0])
	}
	function, ok := stmt.Expression.(*ast.FunctionLiteral)
	if !ok {
		t.Fatalf("stmt.Expression is not ast.FunctionLiteral. got=%T", stmt.Expression)
	}
	if len(function.Parameters) != 2 {
		t.Fatalf("function literal parameters wrong. want 2, got =%d\n", len(function.Parameters))
	}

	testLiteralExpression(t, function.Parameters[0], "x")
	testLiteralExpression(t, function.Parameters[1], "y")

	if len(function.Body.Statements) != 1 {
		t.Fatalf("function.Body.Statements has not 1 statements. got=%d\n", len(function.Body.Statements))
	}

	bodyStmt, ok := function.Body.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("function body stmt is not ast.ExpressionStatement. got=%T", function.Body.Statements[0])
	}
	testInfixExpression(t, bodyStmt.Expression, "x", "+", "y")
}

func TestFunctionParameterParsing(t *testing.T) {
	tests := []struct {
		input          string
		expectedParams []string
	}{
		{input: "fn() {};", expectedParams: []string{}},
		{input: "fn(x){};", expectedParams: []string{"x"}},
		{input: "fn(x,y,z){};", expectedParams: []string{"x", "y", "z"}},
	}

	for _, tt := range tests {
		l := lexer.New(tt.input)
		p := New(l)
		program := p.ParseProgram()
		checkParseErrors(t, p)

		stmt := program.Statements[0].(*ast.ExpressionStatement)
		function := stmt.Expression.(*ast.FunctionLiteral)

		if len(function.Parameters) != len(tt.expectedParams) {
			t.Errorf("length parameters wrong. want %d, got=%d\n",
				len(tt.expectedParams), len(function.Parameters))
		}

		for i, ident := range tt.expectedParams {
			testLiteralExpression(t, function.Parameters[i], ident)
		}
	}
}

func TestCallExpressionParsing(t *testing.T) {
	input := `add(1, 2 * 3, 4+5);`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	if len(program.Statements) != 1 {
		t.Fatalf("program.Statement does not contain %d statements. got=%d\n", 1, len(program.Statements))
	}

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	if !ok {
		t.Fatalf("stmt is not ast.ExpressionStatement. got=%T", program.Statements[0])
	}

	exp, ok := stmt.Expression.(*ast.CallExpression)
	if !ok {
		t.Fatalf("stmt.Expression is not ast.CallExpression. got=%T", stmt.Expression)
	}

	if !testIdentifier(t, exp.Function, "add") {
		return
	}
	if len(exp.Arguments) != 3 {
		t.Fatalf("wrong length arguments. got=%d", len(exp.Arguments))
	}

	testLiteralExpression(t, exp.Arguments[0], 1)
	testInfixExpression(t, exp.Arguments[1], 2, "*", 3)
	testInfixExpression(t, exp.Arguments[2], 4, "+", 5)
}

func TestStringLiteralExpression(t *testing.T) {
	input := `"hello world";`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt := program.Statements[0].(*ast.ExpressionStatement)
	literal, ok := stmt.Expression.(*ast.StringLiteral)
	if !ok {
		t.Fatalf("exp not *ast.StringLiteral. got=%T", stmt.Expression)
	}
	if literal.Value != "hello world" {
		t.Fatalf("literal.Value not %q. got=%q", "hello world", literal.Value)
	}
}

func TestArrayLiteralsParsing(t *testing.T) {
	input := "[1, 2 * 2, 3 + 3]"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	array, ok := stmt.Expression.(*ast.ArrayLiteral)
	if !ok {
		t.Fatalf("exp not ast.ArrayLiteral. got=%T", stmt.Expression)
	}
	if len(array.Element) != 3 {
		t.Fatalf("len(array.Element) not 3. got=%d", len(array.Element))
	}
	testIntegerLiteral(t, array.Element[0], 1)
	testInfixExpression(t, array.Element[1], 2, "*", 2)
	testInfixExpression(t, array.Element[2], 3, "+", 3)
}

func TestIndexExpressionParsing(t *testing.T) {
	input := "myArray[1+1]"

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt, ok := program.Statements[0].(*ast.ExpressionStatement)
	indexExp, ok := stmt.Expression.(*ast.IndexExpression)
	if !ok {
		t.Fatalf("exp not *ast.IndexExpression. got=%T", stmt.Expression)
	}
	if !testIdentifier(t, indexExp.Left, "myArray") {
		return
	}
	if !testInfixExpression(t, indexExp.Index, 1, "+", 1) {
		return
	}
}

func TestHashLiteralParsing(t *testing.T) {
	input := `{"one": 1, "two":2, "three": 3}`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt := program.Statements[0].(*ast.ExpressionStatement)
	hash, ok := stmt.Expression.(*ast.HashLiteral)
	if !ok {
		t.Fatalf("exp is not ast.HashLiteral. got=%T", stmt.Expression)
	}
	if len(hash.Pairs) != 3 {
		t.Errorf("hash.Pairs has wrong length. got=%d", len(hash.Pairs))
	}

	expected := map[string]int64{
		"one":   1,
		"two":   2,
		"three": 3,
	}
	for k, v := range hash.Pairs {
		literal, ok := k.(*ast.StringLiteral)
		if !ok {
			t.Errorf("key is not ast.StringLiteral. got =%T", k)
		}

		expectedVal := expected[literal.String()]
		testIntegerLiteral(t, v, expectedVal)
	}
}

func TestEmptyHashLiteralParsing(t *testing.T) {
	input := `{}`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt := program.Statements[0].(*ast.ExpressionStatement)
	hash, ok := stmt.Expression.(*ast.HashLiteral)
	if !ok {
		t.Fatalf("exp is not ast.HashLiteral. got=%T", stmt.Expression)
	}
	if len(hash.Pairs) != 0 {
		t.Errorf("hash.Pairs has wrong length. got=%d", len(hash.Pairs))
	}
}

func TestParsingHashLiteralsWithExpressions(t *testing.T) {
	input := `{"one": 0 + 1, "two": 10 - 8, "three": 15 / 5}`

	l := lexer.New(input)
	p := New(l)
	program := p.ParseProgram()
	checkParseErrors(t, p)

	stmt := program.Statements[0].(*ast.ExpressionStatement)
	hash, ok := stmt.Expression.(*ast.HashLiteral)
	if !ok {
		t.Fatalf("exp is not ast.HashLiteral. got=%T", stmt.Expression)
	}
	if len(hash.Pairs) != 3 {
		t.Errorf("hash.Pairs has wrong length. got=%d", len(hash.Pairs))
	}

	tests := map[string]func(ast.Expression){
		"one": func(e ast.Expression) {
			testInfixExpression(t, e, 0, "+", 1)
		},
		"two": func(e ast.Expression) {
			testInfixExpression(t, e, 10, "-", 8)
		},
		"three": func(e ast.Expression) {
			testInfixExpression(t, e, 15, "/", 5)
		},
	}

	for key, value := range hash.Pairs {
		literal, ok := key.(*ast.StringLiteral)
		if !ok {
			t.Errorf("key is not ast.StringLiteral. got=%T", key)
			continue
		}

		testFunc, ok := tests[literal.String()]
		if !ok {
			t.Errorf("No test function for key %q found.", literal.String())
			continue
		}
		testFunc(value)
	}
}