Feat: add option to override random generation (#307)

README.md

@@ -415,6 +415,7 @@ You may define following options for `jsf` that alter its behavior:
 - `defaultInvalidTypeProduct`: - default value generated for a schema with invalid type (works only if `failOnInvalidTypes` is set to `false`)
 - `maxItems`: number - Configure a maximum amount of items to generate in an array. This will override the maximum items found inside a JSON Schema.
 - `maxLength`: number - Configure a maximum length to allow generating strings for. This will override the maximum length found inside a JSON Schema.
+- `random`: Function - a replacement for `Math.random` to support pseudorandom number generation.
 
 Set options just as below:
 

package.json

@@ -53,6 +53,7 @@
     "jasmine-node": "2.0.0-beta4",
     "jayschema": "^0.3.1",
     "lodash.template": "^4.4.0",
+    "seedrandom": "^2.4.3",
     "semver": "^5.3.0",
     "tslint": "^4.0.2",
     "tv4": "^1.2.7",

spec/schema/core/option/random.js

+const seedrandom = require('seedrandom');
+
+module.exports = {
+    register: function(jsf) {
+        return jsf.option({
+            random: seedrandom('some seed')
+        });
+    }
+};

spec/schema/core/option/random.json

+[
+  {
+    "description": "random option",
+    "tests": [
+      {
+        "description": "should allow pseudorandom value generation",
+        "schema": {
+          "type": "object",
+          "properties": {
+            "a": {
+              "type": "integer",
+              "minimum": 0,
+              "maximum": 100
+            },
+            "b": {
+              "type": "string"
+            },
+            "c": {
+              "pattern": "^[a-z]{2}[0-9]{3}$"
+            }
+          },
+          "required": ["a", "b", "c"]
+        },
+        "valid": true,
+        "equal": {
+          "a": 39,
+          "b": "dolore et qui ex",
+          "c": "hv837"
+        },
+        "repeat": 1,
+        "require": "core/option/random"
+      }
+    ]
+  }
+]

ts/class/Container.ts

@@ -4,6 +4,10 @@ import option = require('../api/option');
 // set maximum default, see #193
 RandExp.prototype.max = 10;
 
+// same implementation as the original except using our random
+RandExp.prototype.randInt = (a, b) =>
+  a + Math.floor(option('random')() * (1 + b - a));
+
 type Dependency = any;
 
 /**

ts/class/OptionRegistry.ts

 import Registry = require('./Registry');
 
-type Option = boolean|number;
+type Option = boolean|number|Function;
 
 /**
  * This class defines a registry for custom formats used within JSF.
@@ -18,6 +18,7 @@ class OptionRegistry extends Registry<Option> {
     this.data['defaultMinItems'] = 0;
     this.data['defaultRandExpMax'] = 10;
     this.data['alwaysFakeOptionals'] = false;
+    this.data['random'] = Math.random;
   }
 }
 

ts/core/random.ts

 /// <reference path="../index.d.ts" />
 
+var option = require('../api/option');
+
 /**
  * Returns random element of a collection
  *
@@ -7,7 +9,7 @@
  * @returns {T}
  */
 function pick<T>(collection: T[]): T {
-  return collection[Math.floor(Math.random() * collection.length)];
+  return collection[Math.floor(option('random')() * collection.length)];
 }
 
 /**
@@ -23,7 +25,7 @@ function shuffle<T>(collection: T[]): T[] {
     length: number = collection.length;
 
   for (; length > 0;) {
-    key = Math.floor(Math.random() * length);
+    key = Math.floor(option('random')() * length);
     // swap
     tmp = copy[--length];
     copy[length] = copy[key];
@@ -48,7 +50,7 @@ var MIN_NUMBER = -100,
  * @see http://stackoverflow.com/a/1527820/769384
  */
 function getRandomInt(min: number, max: number): number {
-  return Math.floor(Math.random() * (max - min + 1)) + min;
+  return Math.floor(option('random')() * (max - min + 1)) + min;
 }
 
 /**

ts/generators/boolean.ts

+var option = require('../api/option');
+
 /**
  * Generates randomized boolean value.
  *
  * @returns {boolean}
  */
 function booleanGenerator(): boolean {
-  return Math.random() > 0.5;
+  return option('random')() > 0.5;
 }
 
 export = booleanGenerator;

ts/types/string.ts

@@ -55,7 +55,7 @@ var stringType: FTypeGenerator = function stringType(value: IStringSchema): stri
   }
 
   while (output.length < minLength) {
-    output += Math.random() > 0.7 ? thunk() : randexp('.+');
+    output += option('random')() > 0.7 ? thunk() : randexp('.+');
   }
 
   if (output.length > maxLength) {