monkey/internal/lexer/lexer_test.go

package lexer

import (
	"github.com/stretchr/testify/assert"
	"monkey/internal/token"
	"testing"
)

func TestNextToken_Simple(t *testing.T) {
	input := `=+(){},;`
	tests := []struct {
		expectedType    token.TokenType
		expectedLiteral string
	}{
		{token.ASSIGN, "="},
		{token.PLUS, "+"},
		{token.LPAREN, "("},
		{token.RPAREN, ")"},
		{token.LBRACE, "{"},
		{token.RBRACE, "}"},
		{token.COMMA, ","},
		{token.SEMICOLON, ";"},
		{token.EOF, ""},
	}

	l := New(input)
	for i, tt := range tests {
		tok := l.NextToken()
		assert.Equal(t, tt.expectedType, tok.Type, "[%d]: %v %v", i, tok.Type, tt.expectedType)
		assert.Equal(t, tt.expectedLiteral, tok.Literal, "[%d]: %v %v", i, tok.Literal, tt.expectedLiteral)
	}
}

func TestNextToken_Keywords(t *testing.T) {
	input := `fn test() {
		if (5 < 10) {
			return true;
		} else {
			return false;
		}
	}`

	tests := []struct {
		expectedType    token.TokenType
		expectedLiteral string
	}{
		{token.FUNCTION, "fn"},
		{token.IDENT, "test"},
		{token.LPAREN, "("},
		{token.RPAREN, ")"},
		{token.LBRACE, "{"},
		{token.IF, "if"},
		{token.LPAREN, "("},
		{token.INT, "5"},
		{token.LT, "<"},
		{token.INT, "10"},
		{token.RPAREN, ")"},
		{token.LBRACE, "{"},
		{token.RETURN, "return"},
		{token.TRUE, "true"},
		{token.SEMICOLON, ";"},
		{token.RBRACE, "}"},
		{token.ELSE, "else"},
		{token.LBRACE, "{"},
		{token.RETURN, "return"},
		{token.FALSE, "false"},
		{token.SEMICOLON, ";"},
		{token.RBRACE, "}"},
		{token.RBRACE, "}"},
		{token.EOF, ""},
	}

	l := New(input)
	for i, tt := range tests {
		tok := l.NextToken()
		assert.Equal(t, tt.expectedType, tok.Type, "[%d]: %v %v", i, tok.Type, tt.expectedType)
		assert.Equal(t, tt.expectedLiteral, tok.Literal, "[%d]: %v %v", i, tok.Literal, tt.expectedLiteral)
	}
}

func TestNextToken_Complex(t *testing.T) {
	input := `let five = 5;
	let ten = 10;
    let add = fn(x, y) {
		x + y;
	};
    let result = add(five, ten);
	-/*<987>!
	10 == 10
	10 != 9
   `
	tests := []struct {
		expectedType    token.TokenType
		expectedLiteral string
	}{
		{token.LET, "let"},
		{token.IDENT, "five"},
		{token.ASSIGN, "="},
		{token.INT, "5"},
		{token.SEMICOLON, ";"},
		{token.LET, "let"},
		{token.IDENT, "ten"},
		{token.ASSIGN, "="},
		{token.INT, "10"},
		{token.SEMICOLON, ";"},
		{token.LET, "let"},
		{token.IDENT, "add"},
		{token.ASSIGN, "="},
		{token.FUNCTION, "fn"},
		{token.LPAREN, "("},
		{token.IDENT, "x"},
		{token.COMMA, ","},
		{token.IDENT, "y"},
		{token.RPAREN, ")"},
		{token.LBRACE, "{"},
		{token.IDENT, "x"},
		{token.PLUS, "+"},
		{token.IDENT, "y"},
		{token.SEMICOLON, ";"},
		{token.RBRACE, "}"},
		{token.SEMICOLON, ";"},
		{token.LET, "let"},
		{token.IDENT, "result"},
		{token.ASSIGN, "="},
		{token.IDENT, "add"},
		{token.LPAREN, "("},
		{token.IDENT, "five"},
		{token.COMMA, ","},
		{token.IDENT, "ten"},
		{token.RPAREN, ")"},
		{token.SEMICOLON, ";"},
		{token.MINUS, "-"},
		{token.SLASH, "/"},
		{token.ASTERISK, "*"},
		{token.LT, "<"},
		{token.INT, "987"},
		{token.GT, ">"},
		{token.BANG, "!"},
		{token.INT, "10"},
		{token.EQUAL, "=="},
		{token.INT, "10"},
		{token.INT, "10"},
		{token.NEQUAL, "!="},
		{token.INT, "9"},
		{token.EOF, ""},
	}

	l := New(input)
	for i, tt := range tests {
		tok := l.NextToken()
		assert.Equal(t, tt.expectedType, tok.Type, "[%d]: %v %v", i, tok.Type, tt.expectedType)
		assert.Equal(t, tt.expectedLiteral, tok.Literal, "[%d]: %v %v", i, tok.Literal, tt.expectedLiteral)
	}
}