Added some extra test cases for validating empty strings. (#524)

Author: awhitford

test/flutter_form_builder_test.dart

@@ -15,8 +15,10 @@ void main() {
         ],
         home: Builder(
           builder: (BuildContext context) {
-            expect(FormBuilderValidators.required(context)('something long'), isNull);
-            expect(FormBuilderValidators.required(context)(DateTime.now()), isNull);
+            expect(FormBuilderValidators.required(context)('something long'),
+                isNull);
+            expect(FormBuilderValidators.required(context)(DateTime.now()),
+                isNull);
             expect(FormBuilderValidators.required(context)(''), isNotNull);
             expect(FormBuilderValidators.required(context)([]), isNotNull);
 
@@ -38,8 +40,10 @@ void main() {
         ],
         home: Builder(
           builder: (BuildContext context) {
-            expect(FormBuilderValidators.maxLength(context, 5)('something long'), equals('Value must have a length less than or equal to 5'));
-            expect(FormBuilderValidators.maxLength(context, 5)('two'), equals(null));
+            expect(
+                FormBuilderValidators.maxLength(context, 5)('something long'),
+                equals('Value must have a length less than or equal to 5'));
+            expect(FormBuilderValidators.maxLength(context, 5)('two'), isNull);
             // expect(FormBuilderValidators.maxLength(context, 5)(5), equals(null));
 
             // The builder function must return a widget.
@@ -60,13 +64,18 @@ void main() {
         ],
         home: Builder(
           builder: (BuildContext context) {
-            expect(FormBuilderValidators.email(context)('john@flutter'), isNotNull);
-            expect(FormBuilderValidators.email(context)('[email protected]'), isNull);
-            expect(FormBuilderValidators.email(context)(' [email protected] '), isNull);
-            expect(FormBuilderValidators.email(context)('[email protected] '), isNull);
-            expect(FormBuilderValidators.email(context)(' [email protected]'), isNull);
+            expect(FormBuilderValidators.email(context)('john@flutter'),
+                isNotNull);
+            expect(FormBuilderValidators.email(context)('[email protected]'),
+                isNull);
+            expect(FormBuilderValidators.email(context)(' [email protected] '),
+                isNull);
+            expect(FormBuilderValidators.email(context)('[email protected] '),
+                isNull);
+            expect(FormBuilderValidators.email(context)(' [email protected]'),
+                isNull);
             expect(FormBuilderValidators.email(context)(null), isNull);
-            expect(FormBuilderValidators.email(context)(''),isNull);
+            expect(FormBuilderValidators.email(context)(''), isNull);
 
             // The builder function must return a widget.
             return Placeholder();
@@ -87,8 +96,9 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             expect(FormBuilderValidators.max(context, 20)('70'), isNotNull);
-            expect(FormBuilderValidators.max(context,30)(70), isNotNull);
-            expect(FormBuilderValidators.max(context,30)(20), isNull);
+            expect(FormBuilderValidators.max(context, 30)(70), isNotNull);
+            expect(FormBuilderValidators.max(context, 30)(20), isNull);
+            expect(FormBuilderValidators.max(context, 30)(''), isNull);
 
             // The builder function must return a widget.
             return Placeholder();
@@ -108,9 +118,10 @@ void main() {
         ],
         home: Builder(
           builder: (BuildContext context) {
-            expect(FormBuilderValidators.min(context,30)('10'), isNotNull);
-            expect(FormBuilderValidators.min(context,30)(10), isNotNull);
-            expect(FormBuilderValidators.min(context,30)(70), isNull);
+            expect(FormBuilderValidators.min(context, 30)('10'), isNotNull);
+            expect(FormBuilderValidators.min(context, 30)(10), isNotNull);
+            expect(FormBuilderValidators.min(context, 30)(70), isNull);
+            expect(FormBuilderValidators.min(context, 30)(''), isNull);
 
             // The builder function must return a widget.
             return Placeholder();
@@ -131,12 +142,20 @@ void main() {
         home: Builder(
           builder: (BuildContext context) {
             expect(FormBuilderValidators.url(context)(null), isNull);
-            expect(FormBuilderValidators.url(context)('https://www.google.com'), isNull);
-            expect(FormBuilderValidators.url(context)('www.google.com'), isNull);
+            expect(FormBuilderValidators.url(context)('https://www.google.com'),
+                isNull);
+            expect(
+                FormBuilderValidators.url(context)('www.google.com'), isNull);
             expect(FormBuilderValidators.url(context)('google.com'), isNull);
-            expect(FormBuilderValidators.url(context)('http://google.com'), isNull);
+            expect(FormBuilderValidators.url(context)('http://google.com'),
+                isNull);
             expect(FormBuilderValidators.url(context)('.com'), isNotNull);
-            expect(FormBuilderValidators.url(context, protocols: ['https', 'http'], errorText: 'Only HTTP and HTTPS allowed')('ftp://www.google.com'), isNotNull);
+            expect(
+                FormBuilderValidators.url(context,
+                    protocols: ['https', 'http'],
+                    errorText:
+                        'Only HTTP and HTTPS allowed')('ftp://www.google.com'),
+                isNotNull);
 
             // The builder function must return a widget.
             return Placeholder();
@@ -159,6 +178,7 @@ void main() {
             expect(FormBuilderValidators.IP(context)(null), isNull);
             expect(FormBuilderValidators.IP(context)('192.168.0.1'), isNull);
             expect(FormBuilderValidators.IP(context)('256.168.0.1'), isNotNull);
+            expect(FormBuilderValidators.IP(context)(''), isNull);
 
             // The builder function must return a widget.
             return Placeholder();