waiig15/parser/parser_test.go

package parser

import (
	"code.osinet.fr/fgm/waiig15/ast"
	"code.osinet.fr/fgm/waiig15/lexer"
	"testing"
)

func checkParserErrors(t *testing.T, p *Parser) {
	errors := p.Errors()
	if len(errors) == 0 {
		return;
	}

	t.Errorf("parser has %d errors", len(errors))
	for _, msg := range errors {
		t.Errorf("parser error: %q", msg)
	}
	t.FailNow()
}

func TestLetStatements(t *testing.T) {
	// Try removing the ident, the =, or both, to get human-readable errors.
	input := `
let x = 5;
let y = 10;
let foobar = 838383;
`
	l := lexer.New(input)
	p := New(l)

	program := p.ParseProgram()
	checkParserErrors(t, p)
	if program == nil {
		t.Fatalf("ParseProgram() returned nil.")
	}

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

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

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

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
	}

	// Statement is an interface, we need a concrete type for the value, and we
	// just determined this looked like a LetStatement.
	letStmt, ok := s.(*ast.LetStatement)
	if !ok {
		t.Errorf("s not *ast.LetStatement{}, got=%T", s)
	}

	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("letStmt.Name.TokenLiteral not %s, got=%s",
			name, letStmt.Name.TokenLiteral())
		return false
	}

	return true
}