test.js

var superTinyCompiler = require('./super-tiny-compiler');
var assert            = require('assert');

var tokenizer     = superTinyCompiler.tokenizer;
var parser        = superTinyCompiler.parser;
var transformer   = superTinyCompiler.transformer;
var codeGenerator = superTinyCompiler.codeGenerator;
var compiler      = superTinyCompiler.compiler;

var input  = '(add 2 (subtract 4 2))';
var output = 'add(2, subtract(4, 2));';

var tokens = [
  { type: 'paren',  value: '('        },  // paren 意思是括弧（parenthesis）
  { type: 'name',   value: 'add'      },
  { type: 'number', value: '2'        },
  { type: 'paren',  value: '('        },
  { type: 'name',   value: 'subtract' },
  { type: 'number', value: '4'        },
  { type: 'number', value: '2'        },
  { type: 'paren',  value: ')'        },
  { type: 'paren',  value: ')'        }
];

var ast = {       // Abstract Syntax Tree = AST = 抽象语法树
  type: 'Program',
  body: [{
    type: 'CallExpression',
    name: 'add',
    params: [{
      type: 'NumberLiteral',
      value: '2'
    }, {
      type: 'CallExpression',
      name: 'subtract',
      params: [{
        type: 'NumberLiteral',
        value: '4'
      }, {
        type: 'NumberLiteral',
        value: '2'
      }]
    }]
  }]
};

var newAst = {
  type: 'Program',
  body: [{
    type: 'ExpressionStatement',
    expression: {
      type: 'CallExpression',
      callee: {
        type: 'Identifier',
        name: 'add'
      },
      arguments: [{
        type: 'NumberLiteral',
        value: '2'
      }, {
        type: 'CallExpression',
        callee: {
          type: 'Identifier',
          name: 'subtract'
        },
        arguments: [{
          type: 'NumberLiteral',
          value: '4'
        }, {
          type: 'NumberLiteral',
          value: '2'
        }]
      }]
    }
  }]
};

assert.deepStrictEqual(tokenizer(input), tokens, 'Tokenizer should turn `input` string into `tokens` array');
assert.deepStrictEqual(parser(tokens), ast, 'Parser should turn `tokens` array into `ast`');
assert.deepStrictEqual(transformer(ast), newAst, 'Transformer should turn `ast` into a `newAst`');
assert.deepStrictEqual(codeGenerator(newAst), output, 'Code Generator should turn `newAst` into `output` string');
assert.deepStrictEqual(compiler(input), output, 'Compiler should turn `input` into `output`');

console.log();
console.log('测试编译器是否正确的 5 项测试全部通过!');
console.log('编译前: ' + input);
console.log('编译后: ' + compiler(input));
console.log();

/*
console.log 之前那 5 行 assert.deepStrictEqual 是关键

这整个文件就是把编译器的各个部分用手写方式检验是否正确.
先人类分析什么是正确结果, 然后手写正确结果出来, 然后和程序输出的比对一下


assert 是 Node.js 的内置模块，用于断言。如果表达式不符合预期，就抛出一个错误。
拿 assest 的第一行代码举例: 

    assert.deepStrictEqual(tokenizer(input), tokens, 'Tokenizer should turn `input` string into `tokens` array');

前两个参数是要检查的, 如果前两个不一样, 就会报错.
第三个字符串参数是如果出错, 会输出的错误信息.
第三个参数是可选的, 如果不给，默认输出出错的那一行代码

assest 的文档（非常建议看）:
https://nodejs.org/api/assert.html#assert_assert_deepstrictequal_actual_expected_message

*/