monna/parser/parser_test.go

package parser

import (
	"monkey/ast"
	"monkey/lexer"
	"testing"
)

func check_parser_errors(l_test *testing.T, l_parser *Parser) {
	errors := l_parser.Errors()
	if len(errors) == 0 {
		return
	}

	l_test.Errorf("parser has %d errors", len(errors))

	for _, message := range errors {
		l_test.Errorf("parser error: %q", message)
	}
	l_test.FailNow()
}

func TestLetStatement(l_test *testing.T) {
	input := `
   let x = 4;
   let y = 19;
   let foobar = 8948398493;
  `

	l_lexer := lexer.New(input)
	l_parser := New(l_lexer)

	program := l_parser.ParseProgram()
	check_parser_errors(l_test, l_parser)

	if program == nil {
		l_test.Fatalf("ParseProgram() returned nil")
	}

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

	tests := []struct {
		expected_identifier string
	}{
		{"x"},
		{"y"},
		{"foobar"},
	}

	for i, tt := range tests {
		statement := program.Statements[i]
		if !testLetStatement(l_test, statement, tt.expected_identifier) {
			return
		}
	}
}

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

	let_statement, ok := statement.(*ast.LetStatement)
	if !ok {
		l_test.Errorf("statement not *ast.LetStatement, got=%T", statement)
		return false
	}

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

	if let_statement.Name.TokenLiteral() != name {
		l_test.Errorf("let_statement.name.TokenLiteral() not %s, got=%s", name, let_statement.Name.TokenLiteral())
		return false

	}
	return true
}

func TestReturnStatement(l_test *testing.T) {
	input := `
   return 6;
   return 10;
   return 8419849;
  `

	l_lexer := lexer.New(input)
	l_parser := New(l_lexer)

	program := l_parser.ParseProgram()
	check_parser_errors(l_test, l_parser)

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

	for _, statement := range program.Statements {
		return_statement, ok := statement.(*ast.ReturnStatement)

		if !ok {
			l_test.Errorf("statment not *ast.ReturnStatement, got =%T", statement)
			continue
		}

		if return_statement.TokenLiteral() != "return" {
			l_test.Errorf("return_statement.TokenLiteral() not 'return', got %q", return_statement.TokenLiteral())
		}
	}
}