mungedb-aggregate/test/lib/pipeline/expressions/IfNullExpression_test.js

"use strict";
var assert = require("assert"),
	IfNullExpression = require("../../../../lib/pipeline/expressions/IfNullExpression"),
	VariablesParseState = require("../../../../lib/pipeline/expressions/VariablesParseState"),
	VariablesIdGenerator = require("../../../../lib/pipeline/expressions/VariablesIdGenerator"),
	Variables = require("../../../../lib/pipeline/expressions/Variables"),
	Expression = require("../../../../lib/pipeline/expressions/Expression");

// Mocha one-liner to make these tests self-hosted
if(!module.parent)return(require.cache[__filename]=null,(new(require("mocha"))({ui:"exports",reporter:"spec",grep:process.env.TEST_GREP})).addFile(__filename).run(process.exit));

exports.IfNullExpression = {

	"constructor()": {

		"should not throw Error when constructing without args": function() {
			assert.doesNotThrow(function () {
				new IfNullExpression();
			});
		},

		"should throw Error when constructing with args": function () {
			assert.throws(function () {
				new IfNullExpression(1);
			});
		},

	},

	"#getOpName()": {

		"should return the correct op name; $ifNull": function() {
			assert.equal(new IfNullExpression().getOpName(), "$ifNull");
		},

	},

	"#evaluate()": {

		beforeEach: function () {
			this.vps = new VariablesParseState(new VariablesIdGenerator());
			this.parsed = Expression.parseExpression("$ifNull", ["$a", "$b"], this.vps);
		},

		"should return the left hand side if the left hand side is not null or undefined": function() {
			assert.strictEqual(this.parsed.evaluate({a: 1, b: 2}), 1);
		},

		"should return the right hand side if the left hand side is null": function() {
			assert.strictEqual(this.parsed.evaluate({a: null, b: 2}), 2);
		},

		"should return the right hand side if the left hand side is undefined": function() {
			assert.strictEqual(this.parsed.evaluate({b: 2}), 2);
		},

	},

};