Add 'throws'/'notThrows' assertion to Ospec for error reporting (#2255)

* Ospec: added assertion that function does/doesnt throw error

* Ospec.throws passes npm test

* Ospec.throws: Address requested changes

* Ospec: message comparison support for .throws/.notthrows

Credit to @maranomynet, #2227

ospec/README.md

@@ -429,7 +429,7 @@ If an argument is defined for the `assertions` function, the test is deemed to b
 
 ### Assertion o(any value)
 
-Starts an assertion. There are four types of assertion: `equals`, `notEquals`, `deepEquals` and `notDeepEquals`.
+Starts an assertion. There are six types of assertion: `equals`, `notEquals`, `deepEquals`, `notDeepEquals`, `throws`, `notThrows`.
 
 Assertions have this form:
 
@@ -467,6 +467,22 @@ Asserts that two values are recursively equal
 
 Asserts that two values are not recursively equal
 
+#### Function(String description) o(Function fn).throws(Object constructor)
+
+Asserts that a function throws an instance of the provided constructo
+
+#### Function(String description) o(Function fn).throws(String message)
+
+Asserts that a function throws an Error with the provided message
+
+#### Function(String description) o(Function fn).notThrows(Object constructor)
+
+Asserts that a function does not throw an instance of the provided constructor
+
+#### Function(String description) o(Function fn).notThrows(String message)
+
+Asserts that a function does not throw an Error with the provided message
+
 ---
 
 ### void o.before(Function([Function done [, Function timeout]]) setup)

ospec/change-log.md

@@ -5,6 +5,7 @@
 _2018-xx-yy_
 <!-- Add new lines here. Version number will be decided later -->
 - Add `spy.calls` array property to get the `this` and `arguments` values for any arbitrary call.
+- Added `.throws` and `.notThrows` assertions to ospec. (#2255 @robertakarobin)
 
 ## 3.0.1
 _2018-06-30_

ospec/ospec.js

@@ -220,6 +220,8 @@ else window.o = m()
 	define("notEquals", "should not equal", function(a, b) {return a !== b})
 	define("deepEquals", "should deep equal", deepEqual)
 	define("notDeepEquals", "should not deep equal", function(a, b) {return !deepEqual(a, b)})
+	define("throws", "should throw a", throws)
+	define("notThrows", "should not throw a", function(a, b) {return !throws(a, b)})
 
 	function isArguments(a) {
 		if ("callee" in a) {
@@ -260,6 +262,18 @@ else window.o = m()
 		}
 		return false
 	}
+	function throws(a, b){
+		try{
+			a()
+		}catch(e){
+			if(typeof b === "string"){
+				return (e.message === b)
+			}else{
+				return (e instanceof b)
+			}
+		}
+		return false
+	}
 
 	function isRunning() {return results != null}
 	function Assert(value) {

ospec/tests/test-ospec.js

@@ -163,6 +163,14 @@ o.spec("ospec", function() {
 			o(a).notEquals(2)
 			o({a: [1, 2], b: 3}).deepEquals({a: [1, 2], b: 3})
 			o([{a: 1, b: 2}, {c: 3}]).deepEquals([{a: 1, b: 2}, {c: 3}])
+			o(function(){throw new Error()}).throws(Error)
+			o(function(){"ayy".foo()}).throws(TypeError)
+			o(function(){Math.PI.toFixed(Math.pow(10,20))}).throws(RangeError)
+			o(function(){decodeURIComponent("%")}).throws(URIError)
+
+			o(function(){"ayy".foo()}).notThrows(SyntaxError)
+			o(function(){throw new Error("foo")}).throws("foo")
+			o(function(){throw new Error("foo")}).notThrows("bar")
 
 			var undef1 = {undef: void 0}
 			var undef2 = {UNDEF: void 0}