Added tests for PR #122 (amendable)

Note though that this test case

 - is not Node 4 compatible since the plugin is not Node 4 compatible
 - might not be reliably since the regression case depends on postcss'
   and postcss-preset-env's internal workings and might be
   false-positive (false-non-failing) when there's actually an error.

Gruntfile.js

@@ -103,6 +103,31 @@ module.exports = function(grunt) {
                 },
                 src: 'test/fixtures/a.scss',
                 dest: 'tmp/noWriteDest.scss'
+            },
+            ensureSequentialRun1: {
+                options: {
+                    processors: [require("postcss-preset-env")]
+                },
+                files: [{
+                    src: 'test/fixtures/b1.css',
+                    dest: 'tmp/ensureSequentialRun1sequence1.css'
+                }, {
+                    src: 'test/fixtures/b2.css',
+                    dest: 'tmp/ensureSequentialRun2sequence1.css'
+                }]
+            },
+            // Same issue, different order. The result shall be the same
+            ensureSequentialRun2: {
+                options: {
+                    processors: [require("postcss-preset-env")]
+                },
+                files: [{
+                    src: 'test/fixtures/b2.css',
+                    dest: 'tmp/ensureSequentialRun2sequence2.css'
+                }, {
+                    src: 'test/fixtures/b1.css',
+                    dest: 'tmp/ensureSequentialRun1sequence2.css'
+                }]
             }
         },
 

package.json

@@ -37,6 +37,7 @@
     "grunt-contrib-jshint": "^1.0.0",
     "grunt-contrib-nodeunit": "^1.0.0",
     "load-grunt-tasks": "^3.1.0",
+    "postcss-preset-env": "^6.6.0",
     "postcss-scss": "^1.0.2",
     "time-grunt": "^1.1.0"
   },

test/expected/ensureSequentialRun1.css

@@ -0,0 +1,9 @@
+
+:root {
+	--foo: #333;
+}
+
+.moo {
+	color: #333;
+	color: var(--foo);
+}

test/expected/ensureSequentialRun2.css

@@ -0,0 +1,4 @@
+
+:root {
+	--foo: #666;
+}

test/fixtures/b1.css

@@ -0,0 +1,8 @@
+
+:root {
+	--foo: #333;
+}
+
+.moo {
+	color: var(--foo);
+}

test/fixtures/b2.css

@@ -0,0 +1,4 @@
+
+:root {
+	--foo: #666;
+}

test/test.js

@@ -133,4 +133,37 @@ exports.gruntPostcss = {
         test.ok(!grunt.file.exists('tmp/noWriteDest.scss'));
         test.done();
     },
+
+    ensureSequentialRun1: function(test) {
+        var actual = {
+            css1: grunt.file.read('tmp/ensureSequentialRun1sequence1.css'),
+            css2: grunt.file.read('tmp/ensureSequentialRun2sequence1.css')
+        };
+
+        var expected = {
+            css1: grunt.file.read('test/expected/ensureSequentialRun1.css'),
+            css2: grunt.file.read('test/expected/ensureSequentialRun2.css'),
+        };
+
+        test.strictEqual(actual.css1, expected.css1);
+        test.strictEqual(actual.css2, expected.css2);
+        test.done();
+    },
+
+    // Identical validation
+    ensureSequentialRun2: function(test) {
+        var actual = {
+            css1: grunt.file.read('tmp/ensureSequentialRun1sequence2.css'),
+            css2: grunt.file.read('tmp/ensureSequentialRun2sequence2.css')
+        };
+
+        var expected = {
+            css1: grunt.file.read('test/expected/ensureSequentialRun1.css'),
+            css2: grunt.file.read('test/expected/ensureSequentialRun2.css'),
+        };
+
+        test.strictEqual(actual.css1, expected.css1);
+        test.strictEqual(actual.css2, expected.css2);
+        test.done();
+    },
 };