Added test to check if the previous month button is enabled if the cu…

…rrent month is after the minDate month prop

test/date-picker/calendar-spec.js

@@ -120,4 +120,20 @@ describe(`Calendar`, () => {
 
         expect(calendarToolbar.props.prevMonth).to.be.false;
     });
+
+    it(`should enable the previous month button if the current month is after the minDate month prop`, () => {
+        let initialDate = new Date();
+        let minDate = new Date(initialDate.toDateString());
+        minDate.setMonth(initialDate.getMonth() - 1);
+
+        let render = TestUtils.renderIntoDocument(
+            <ThemedCalendar 
+                initialDate={initialDate}
+                minDate={minDate} 
+            />
+        );
+        let calendarToolbar = TestUtils.findRenderedComponentWithType(render, CalendarToolbar);
+
+        expect(calendarToolbar.props.prevMonth).to.be.true;
+    });
 });