chore(tests): add jest and tests

package.json

@@ -17,10 +17,12 @@
   ],
   "scripts": {
     "version": "auto-changelog -p --template keepachangelog && git add CHANGELOG.md",
-    "prepublishOnly": "git push && git push --tags && gh-release"
+    "prepublishOnly": "git push && git push --tags && gh-release",
+    "test": "jest"
   },
   "devDependencies": {
     "auto-changelog": "^2.0.0",
-    "gh-release": "^3.5.0"
+    "gh-release": "^3.5.0",
+    "jest": "^25.3.0"
   }
 }

src/index.js

@@ -1,7 +1,6 @@
-const fs = require("fs");
-const util = require("util")
-
-const pWriteFile = util.promisify(fs.writeFile)
+const fs = require('fs');
+const util = require('util');
+const pWriteFile = util.promisify(fs.writeFile);
 
 /**
  * Overrides an ENV var with a value if it exists
@@ -16,23 +15,30 @@ function setEnvWithValue(key, contextOrBranch, mode) {
     return;
   }
 
-  console.log(`Setting ${key} to the value from ${envVar}.`);
-  process.env[key] = process.env[envVar];
+  console.log(`Exporting ${key}=${process.env[envVar]}.`);
+
+  // Renable this once setting process.env is supported in Netlify builds
+  // See: https://github.com/netlify/build/issues/1129
+  // process.env[key] = process.env[envVar];
   return `${key}=${process.env[envVar]}\n`;
 }
 
 module.exports = {
   onPreBuild: async ({ inputs }) => {
-    const context = `${process.env.CONTEXT}`.toUpperCase().replace(/-/g, "_");
-    const branch = `${process.env.BRANCH}`.toUpperCase().replace(/-/g, "_");
+    const context = `${process.env.CONTEXT}`.toUpperCase().replace(/-/g, '_');
+    const branch = `${process.env.BRANCH}`.toUpperCase().replace(/-/g, '_');
 
-    const replaced = [].concat(...Object.keys(process.env)
-      .map((key) => [setEnvWithValue(key, context, inputs.mode), setEnvWithValue(key, branch, inputs.mode)])
-    ).filter(Boolean)
+    const envOverrides = Object.keys(process.env).map((key) => [
+      setEnvWithValue(key, context, inputs.mode),
+      setEnvWithValue(key, branch, inputs.mode),
+    ]);
+
+    const replaced = [].concat(...envOverrides).filter(Boolean);
 
     if (replaced.length) {
       // Write an env file so we can source it during build
-      await pWriteFile(".env", replaced.join(""))
+      await pWriteFile('.env', replaced.join(''));
+
       console.log(`Replaced ${replaced.length} ENVs and wrote .env file`);
     } else {
       console.log(`Nothing found... keeping default ENVs`);

src/index.test.js

@@ -0,0 +1,76 @@
+jest.mock('fs');
+const mockWriteFile = jest.fn(() => Promise.resolve());
+
+jest.mock('util', () => ({
+  promisify: () => mockWriteFile,
+}));
+
+const onPreBuild = require('./index').onPreBuild;
+
+describe('onPreBuild', () => {
+  const OLD_ENV = process.env;
+
+  beforeEach(() => {
+    mockWriteFile.mockReset();
+    jest.resetModules();
+    process.env = { ...OLD_ENV };
+  });
+
+  afterEach(() => {
+    process.env = OLD_ENV;
+  });
+
+  describe('with context prefix ENV overrides', () => {
+    it('writes an env file with updated values', async () => {
+      process.env.DATABASE_URL = 'https://dev.com';
+      process.env.STAGING_DATABASE_URL = 'https://stage.com';
+      process.env.CONTEXT = 'staging';
+      await onPreBuild({ inputs: { mode: 'prefix' } });
+
+      expect(mockWriteFile).toHaveBeenCalledWith('.env', 'DATABASE_URL=https://stage.com\n');
+    });
+  });
+
+  describe('with suffix context prefix ENV overrides', () => {
+    it('writes an env file with updated values', async () => {
+      process.env.DATABASE_URL = 'https://dev.com';
+      process.env.DATABASE_URL_STAGING = 'https://stage.com';
+      process.env.CONTEXT = 'staging';
+      await onPreBuild({ inputs: { mode: 'suffix' } });
+
+      expect(mockWriteFile).toHaveBeenCalledWith('.env', 'DATABASE_URL=https://stage.com\n');
+    });
+  });
+
+  describe('with branch ENV overrides', () => {
+    it('writes an env file with updated values', async () => {
+      process.env.DATABASE_URL = 'https://dev.com';
+      process.env.HELLO_DATABASE_URL = 'https://stage.com';
+      process.env.BRANCH = 'hello';
+      await onPreBuild({ inputs: { mode: 'prefix' } });
+
+      expect(mockWriteFile).toHaveBeenCalledWith('.env', 'DATABASE_URL=https://stage.com\n');
+    });
+  });
+
+  describe('with suffix branch ENV overrides', () => {
+    it('writes an env file with updated values', async () => {
+      process.env.DATABASE_URL = 'https://dev.com';
+      process.env.DATABASE_URL_HELLO = 'https://stage.com';
+      process.env.BRANCH = 'hello';
+      await onPreBuild({ inputs: { mode: 'suffix' } });
+
+      expect(mockWriteFile).toHaveBeenCalledWith('.env', 'DATABASE_URL=https://stage.com\n');
+    });
+  });
+
+  describe('without ENV overrides', () => {
+    it('writes an env file with updated values', async () => {
+      process.env.DATABASE_URL = 'https://dev.com';
+      process.env.BRANCH = 'hello';
+      await onPreBuild({ inputs: { mode: 'prefix' } });
+
+      expect(mockWriteFile).not.toHaveBeenCalled();
+    });
+  });
+});