Allow configuring custom web3 instance (#38)

* add web3-utils as a dependency

* rename main file to index.js

* add explicit web3 injection with global fallback

* change installation procedure for integration tests

* add integration test for using in migrations

* emit better error message on migration integration test

* add version check to web3 injection

* allow multiple injection of the same instance

* tweak migration integration test

* fix linter errors

* pin web3-utils to beta 37

* remove leftover comment

* rename integration test

* add truffle-migration test to travis

* keep test directory

* make inject-web3 a configuration step instead of alternative entry point

* remove unnecessary npm install

* move default configuration logic to configure.js

* rename global-web3 to configure-web3

* add changelog entry

* add note about configuration in README

* fix linter errors

* Revert "remove unnecessary npm install"

This reverts commit a918899.

* configure eslint globals correctly

* fix some parentheses

.eslintrc

@@ -13,12 +13,6 @@
     "mocha"   : true,
     "jest"    : true,
   },
-  "globals" : {
-    "artifacts": false,
-    "contract": false,
-    "assert": false,
-    "web3": false,
-  },
   "rules": {
 
     // Strict mode

.travis.yml

@@ -28,6 +28,11 @@ jobs:
       name: "Ganache Core 2.1.x"
       script: ./test-integration/ganache-core-2.1.x/run.sh
 
+    - stage: Integration tests
+      name: "Truffle Migration"
+      script: ./test-integration/truffle-migration/run.sh
+
+
 notifications:
   slack:
     rooms:

CHANGELOG.md

@@ -5,6 +5,7 @@
  * Fix `send.transaction` not working on contracts with a fallback function. ([#26](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/26)
  * `shouldFail.reverting.withMessage` fails if no error string is provided. ([#28](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/28)
  * Rename `makeInterfaceId` to `makeInterfaceId.ERC165`, and add `makeInterfaceId.ERC1820`. ([#21](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/21)
+ * Add possibility to configure a custom web3 instance. ([#38](https://github.com/OpenZeppelin/openzeppelin-test-helpers/pull/38))
 
 #### How to upgrade from 0.3
 - Change all occurences of `makeInterfaceId` to `makeInterfaceId.ERC165`.

README.md

@@ -47,6 +47,16 @@ contract('ERC20', ([sender, receiver]) => {
 });
 ```
 
+### Configuration
+
+By default, this library will look for a global web3 instance, but you can run a manual configuration and supply a custom one.
+
+```javascript
+require('openzeppelin-test-helpers/configure')({ web3: ... });
+
+const { expectEvent } = require('openzeppelin-test-helpers');
+```
+
 ## Reference
 
 This documentation is a work in progress: if in doubt, head over to the [tests directory](https://github.com/OpenZeppelin/openzeppelin-test-helpers/tree/master/test/src) to see examples of how each helper can be used.

configure.js

@@ -0,0 +1,55 @@
+/* global web3 */
+
+const { setWeb3 } = require('./src/configure-web3');
+
+let loadedConfig;
+
+function configure (config) {
+  if (!config) {
+    // if there already is a loaded config keep it
+    if (!loadedConfig) {
+      defaultConfigure();
+      loadedConfig = 'default';
+    }
+  } else {
+    if (loadedConfig) {
+      let errorMessage = 'Cannot configure openzeppelin-test-helpers a second time.';
+
+      if (loadedConfig === 'default') {
+        errorMessage += `
+
+A configuration has been loaded by default. Make sure to do custom configuration before importing the library.
+
+    require('openzeppelin-test-helpers/configure')({ web3: ... });
+    const { expectEvent } = require('openzeppelin-test-helpers');
+
+`;
+      }
+
+      throw new Error(errorMessage);
+    }
+
+    customConfigure(config);
+    loadedConfig = 'custom';
+  }
+};
+
+function defaultConfigure () {
+  if (typeof web3 === 'undefined') {
+    throw new Error(`Cannot find a global Web3 instance. Please configure one manually:
+
+    require('openzeppelin-test-helpers/configure')({ web3: ... });
+
+`
+    );
+  }
+
+  // use global web3
+  setWeb3(web3);
+}
+
+function customConfigure (config) {
+  setWeb3(config.web3);
+}
+
+module.exports = configure;