Add tests for context of filters

test/node_modules/gitbook-plugin-test-filters/index.js

@@ -0,0 +1,21 @@
+var should = require('should');
+
+module.exports = {
+    filters: {
+        // Simple test
+        hello: function(s) {
+            return 'Hello ' + s + '!';
+        },
+
+        // Test using the conetxt "this"
+        testContext: function(s) {
+            this.should.have.property('config');
+            this.should.have.property('log');
+            this.should.have.property('options');
+            this.should.have.property('resolve').which.is.a.function;
+            this.should.have.property('book').which.equal(this);
+
+            return 'Hello ' + s + '!';
+        }
+    }
+};

test/node_modules/gitbook-plugin-test-filters/package.json

@@ -0,0 +1,7 @@
+{
+    "name": "gitbook-plugin-test-filters",
+    "version": "1.0.0",
+    "engines": {
+        "gitbook": "*"
+    }
+}