Add unit test cases

pubspec.yaml

@@ -6,3 +6,6 @@ homepage: https://github.com/pd4d10/nanoid
 
 environment:
   sdk: ">=2.0.0-dev.32.0 <2.0.0"
+
+dev_dependencies:
+  test: ^0.12.33

test/generate_test.dart

@@ -0,0 +1,29 @@
+import 'package:test/test.dart';
+import 'package:nanoid/generate.dart';
+
+void main() {
+  test('has options', () {
+    expect(generate('a', 5), equals('aaaaa'));
+  });
+
+  test('has flat distribution', () {
+    var COUNT = 100 * 1000;
+    var LENGTH = 5;
+    var ALPHABET = 'abcdefghijklmnopqrstuvwxyz';
+
+    var chars = {};
+    for (var i = 0; i < COUNT; i++) {
+      var id = generate(ALPHABET, LENGTH);
+      for (var j = 0; j < id.length; j++) {
+        var char = id[j];
+        if (chars[char] == null) chars[char] = 0;
+        chars[char] += 1;
+      }
+    }
+
+    chars.forEach((k, _) {
+      var distribution = (chars[k] * ALPHABET.length) / (COUNT * LENGTH);
+      expect(distribution, closeTo(1, 1));
+    });
+  });
+}

test/nanoid_test.dart

@@ -0,0 +1,25 @@
+import 'package:test/test.dart';
+import 'package:nanoid/nanoid.dart';
+import 'package:nanoid/url.dart';
+
+void main() {
+  test('generates URL-friendly IDs', () {
+    for (var i = 0; i < 10; i++) {
+      var id = nanoid();
+      expect(id.length, equals(21));
+      for (var j = 0; j < id.length; j++) {
+        expect(url.contains(id[j]), equals(true));
+      }
+    }
+  });
+
+  test('has no collisions', () {
+    var COUNT = 100 * 1000;
+    var used = {};
+    for (var i = 0; i < COUNT; i++) {
+      var id = nanoid();
+      expect(used[id], equals(null));
+      used[id] = true;
+    }
+  });
+}