diff --git a/test/configs/config.config.js b/test/configs/config.config.js
new file mode 100644
index 00000000..a6246564
--- /dev/null
+++ b/test/configs/config.config.js
@@ -0,0 +1,9 @@
+module.exports = {
+  file: 'config',
+  options: {
+    config: {
+      path: 'test/fixtures/config/postcss.config.js',
+      ctx: { plugin: false }
+    }
+  }
+}
diff --git a/test/configs/config.json b/test/configs/config.json
deleted file mode 100644
index 10ccd687..00000000
--- a/test/configs/config.json
+++ /dev/null
@@ -1,9 +0,0 @@
-{
-  "file": "config",
-  "options": {
-    "config": {
-      "path": "test/fixtures/config/postcss.config.js",
-      "ctx": { "plugin": false }
-    }
-  }
-}
diff --git a/test/configs/error.config.js b/test/configs/error.config.js
new file mode 100644
index 00000000..546e53c6
--- /dev/null
+++ b/test/configs/error.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'error',
+  options: {
+    parser: 'sugarss'
+  }
+}
diff --git a/test/configs/error.json b/test/configs/error.json
deleted file mode 100644
index b09fb918..00000000
--- a/test/configs/error.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "error",
-  "options": {
-    "parser": "sugarss"
-  }
-}
diff --git a/test/configs/exec.config.js b/test/configs/exec.config.js
new file mode 100644
index 00000000..edcc7bd1
--- /dev/null
+++ b/test/configs/exec.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'exec',
+  options: {
+    exec: true
+  }
+}
diff --git a/test/configs/exec.json b/test/configs/exec.json
deleted file mode 100644
index 0c07dd74..00000000
--- a/test/configs/exec.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "exec",
-  "options": {
-    "exec": true
-  }
-}
diff --git a/test/configs/export.config.js b/test/configs/export.config.js
new file mode 100644
index 00000000..f9183a8f
--- /dev/null
+++ b/test/configs/export.config.js
@@ -0,0 +1,8 @@
+module.exports = {
+  file: 'export',
+  options: {
+    config: {
+      path: 'test/fixtures/config/postcss.config.js'
+    }
+  }
+}
diff --git a/test/configs/export.json b/test/configs/export.json
deleted file mode 100644
index dce71c49..00000000
--- a/test/configs/export.json
+++ /dev/null
@@ -1,8 +0,0 @@
-{
-  "file": "export",
-  "options": {
-    "config": {
-      "path": "test/fixtures/config/postcss.config.js"
-    }
-  }
-}
diff --git a/test/configs/jss.config.js b/test/configs/jss.config.js
new file mode 100644
index 00000000..a623a8d5
--- /dev/null
+++ b/test/configs/jss.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'jss',
+  options: {
+    parser: 'postcss-js'
+  }
+}
diff --git a/test/configs/jss.json b/test/configs/jss.json
deleted file mode 100644
index c971af37..00000000
--- a/test/configs/jss.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "jss",
-  "options": {
-    "parser": "postcss-js"
-  }
-}
diff --git a/test/configs/map.config.js b/test/configs/map.config.js
new file mode 100644
index 00000000..939a4cb8
--- /dev/null
+++ b/test/configs/map.config.js
@@ -0,0 +1,9 @@
+module.exports = {
+  file: 'map',
+  options: {
+    config: {
+      path: 'test/fixtures'
+    },
+    sourceMap: 'inline'
+  }
+}
diff --git a/test/configs/map.json b/test/configs/map.json
deleted file mode 100644
index ba535545..00000000
--- a/test/configs/map.json
+++ /dev/null
@@ -1,9 +0,0 @@
-{
-  "file": "map",
-  "options": {
-    "config": {
-      "path": "test/fixtures"
-    },
-    "sourceMap": "inline"
-  }
-}
diff --git a/test/configs/options.config.js b/test/configs/options.config.js
new file mode 100644
index 00000000..c5078019
--- /dev/null
+++ b/test/configs/options.config.js
@@ -0,0 +1,8 @@
+module.exports = {
+  file: 'options',
+  options: {
+    parser: {},
+    syntax: [],
+    plugins: {}
+  }
+}
diff --git a/test/configs/options.json b/test/configs/options.json
deleted file mode 100644
index 55b9f36e..00000000
--- a/test/configs/options.json
+++ /dev/null
@@ -1,8 +0,0 @@
-{
-  "file": "options",
-  "options": {
-    "parser": {},
-    "syntax": [],
-    "plugins": {}
-  }
-}
diff --git a/test/configs/parser.config.js b/test/configs/parser.config.js
new file mode 100644
index 00000000..f0848776
--- /dev/null
+++ b/test/configs/parser.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'parser',
+  options: {
+    parser: 'sugarss'
+  }
+}
diff --git a/test/configs/parser.json b/test/configs/parser.json
deleted file mode 100644
index 9df7d574..00000000
--- a/test/configs/parser.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "parser",
-  "options": {
-    "parser": "sugarss"
-  }
-}
diff --git a/test/configs/plugins.config.js b/test/configs/plugins.config.js
new file mode 100644
index 00000000..f62da8a4
--- /dev/null
+++ b/test/configs/plugins.config.js
@@ -0,0 +1,8 @@
+module.exports = {
+  file: 'plugins',
+  options: {
+    plugins: [
+      require('../plugin')()
+    ]
+  }
+}
diff --git a/test/configs/plugins.fn.config.js b/test/configs/plugins.fn.config.js
new file mode 100644
index 00000000..706e15ef
--- /dev/null
+++ b/test/configs/plugins.fn.config.js
@@ -0,0 +1,8 @@
+module.exports = {
+  file: 'plugins.fn',
+  options: {
+    plugins: () => [
+      require('../plugin')()
+    ]
+  }
+}
diff --git a/test/configs/plugins.fn.js b/test/configs/plugins.fn.js
new file mode 100644
index 00000000..ab1a5337
--- /dev/null
+++ b/test/configs/plugins.fn.js
@@ -0,0 +1,4 @@
+test('Plugins - {Function}', () => {
+  const css = require('../fixtures/style.css')
+  expect(css).toEqual('a { color: rgba(255, 0, 0, 1.0) }\n')
+})
diff --git a/test/configs/plugins.json b/test/configs/plugins.json
deleted file mode 100644
index f87fa371..00000000
--- a/test/configs/plugins.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "plugins",
-  "options": {
-    "plugins": true
-  }
-}
diff --git a/test/configs/sourceMap-inline.config.js b/test/configs/sourceMap-inline.config.js
new file mode 100644
index 00000000..164fa621
--- /dev/null
+++ b/test/configs/sourceMap-inline.config.js
@@ -0,0 +1,9 @@
+module.exports = {
+  file: 'sourceMap-inline',
+  options: {
+    config: {
+      path: 'test/fixtures/config/postcss.config.js'
+    },
+    sourceMap: 'inline'
+  }
+}
diff --git a/test/configs/sourceMap-inline.js b/test/configs/sourceMap-inline.js
new file mode 100644
index 00000000..1c9fb04b
--- /dev/null
+++ b/test/configs/sourceMap-inline.js
@@ -0,0 +1,4 @@
+test('Source Maps - Inline', () => {
+  const css = require('../fixtures/style.css')
+  expect(css).toEqual('a { color: black }\n\n/*# sourceMappingURL=data:application/json;base64,eyJ2ZXJzaW9uIjozLCJzb3VyY2VzIjpbInN0eWxlLmNzcyJdLCJuYW1lcyI6W10sIm1hcHBpbmdzIjoiQUFBQSxJQUFJLFlBQVksRUFBRSIsImZpbGUiOiJzdHlsZS5jc3MiLCJzb3VyY2VzQ29udGVudCI6WyJhIHsgY29sb3I6IGJsYWNrIH1cbiJdfQ== */')
+})
diff --git a/test/configs/sourceMap-true.config.js b/test/configs/sourceMap-true.config.js
new file mode 100644
index 00000000..1ef81ab9
--- /dev/null
+++ b/test/configs/sourceMap-true.config.js
@@ -0,0 +1,9 @@
+module.exports = {
+  file: 'sourceMap-true',
+  options: {
+    config: {
+      path: 'test/fixtures/config/postcss.config.js'
+    },
+    sourceMap: true
+  }
+}
diff --git a/test/configs/sourceMap.js b/test/configs/sourceMap-true.js
similarity index 73%
rename from test/configs/sourceMap.js
rename to test/configs/sourceMap-true.js
index d6398d98..44e4079b 100644
--- a/test/configs/sourceMap.js
+++ b/test/configs/sourceMap-true.js
@@ -1,4 +1,4 @@
-test('Source Maps', () => {
+test('Source Maps - true', () => {
   const css = require('../fixtures/style.css')
   expect(css).toEqual('a { color: black }\n')
 })
diff --git a/test/configs/sourceMap.json b/test/configs/sourceMap.json
deleted file mode 100644
index a245f5f7..00000000
--- a/test/configs/sourceMap.json
+++ /dev/null
@@ -1,9 +0,0 @@
-{
-  "file": "sourceMap",
-  "options": {
-    "config": {
-      "path": "test/fixtures/config/postcss.config.js"
-    },
-    "sourceMap": true
-  }
-}
diff --git a/test/configs/stringifier.config.js b/test/configs/stringifier.config.js
new file mode 100644
index 00000000..5edf499e
--- /dev/null
+++ b/test/configs/stringifier.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'stringifier',
+  options: {
+    stringifier: 'sugarss'
+  }
+}
diff --git a/test/configs/stringifier.json b/test/configs/stringifier.json
deleted file mode 100644
index 47f06f81..00000000
--- a/test/configs/stringifier.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "stringifier",
-  "options": {
-    "stringifier": "sugarss"
-  }
-}
diff --git a/test/configs/syntax.config.js b/test/configs/syntax.config.js
new file mode 100644
index 00000000..5265a8be
--- /dev/null
+++ b/test/configs/syntax.config.js
@@ -0,0 +1,6 @@
+module.exports = {
+  file: 'syntax',
+  options: {
+    syntax: 'sugarss'
+  }
+}
diff --git a/test/configs/syntax.json b/test/configs/syntax.json
deleted file mode 100644
index 83ac0874..00000000
--- a/test/configs/syntax.json
+++ /dev/null
@@ -1,6 +0,0 @@
-{
-  "file": "syntax",
-  "options": {
-    "syntax": "sugarss"
-  }
-}
diff --git a/test/webpack.build.js b/test/webpack.build.js
index 98631156..443b24b2 100644
--- a/test/webpack.build.js
+++ b/test/webpack.build.js
@@ -10,9 +10,9 @@ const builds = path.join(__dirname, 'builds')
 if (fs.existsSync(builds)) fs.remove(builds)
 
 fs.readdirSync(path.join(__dirname, 'configs'))
-  .filter((file) => path.extname(file) === '.json')
+  .filter((file) => path.extname(file) === '.js' && path.extname(path.basename(file, '.js')) === '.config')
   .forEach((config) => {
-    config = fs.readFileSync(path.join(__dirname, 'configs', config), 'utf8')
+    config = require(path.join(__dirname, 'configs', config))
     config = require(path.join(__dirname, 'webpack.config.js'))(config)
 
     webpack(config, () => {})
diff --git a/test/webpack.config.js b/test/webpack.config.js
index a90b2dfa..faae2ec6 100644
--- a/test/webpack.config.js
+++ b/test/webpack.config.js
@@ -3,12 +3,6 @@
 const path = require('path')
 
 module.exports = (config) => {
-  config = JSON.parse(config)
-
-  if (config.options && config.options.plugins) {
-    config.options.plugins = [ require('./plugin')() ]
-  }
-
   return {
     target: 'node',
     devtool: 'source-map',