add failing tests to prevent regression

Author: trevdor

__tests__/components/Headers/TimelineHeader.test.js

@@ -68,13 +68,27 @@ describe('TimelineHeader', () => {
     expect(getByTestId('headerContainer')).toHaveClass('testClassName')
   })
 
+  it('Given TimelineHeader When no calendarHeaderClassName specified Then undefined should not be applied to the date header container', () => {
+    const { getByTestId } = renderTimelineWithLeftAndRightSidebar({
+      calendarHeaderClassName: undefined
+    })
+    expect(getByTestId('headerContainer')).not.toHaveClass('undefined')
+  })
+
   it('Given TimelineHeader When pass className Then it should be applied to the root header container', () => {
     const { getByTestId } = renderTimelineWithLeftAndRightSidebar({
       className: 'testClassName'
     })
     expect(getByTestId('headerRootDiv')).toHaveClass('testClassName')
   })
 
+  it('Given TimelineHeader When no className specified Then undefined should not be applied to the root header container', () => {
+    const { getByTestId } = renderTimelineWithLeftAndRightSidebar({
+      className: undefined
+    })
+    expect(getByTestId('headerRootDiv')).not.toHaveClass('undefined')
+  })
+
   it('Given TimelineHeader When rendered Then it should render the default styles of the date header container', () => {
     const { getByTestId } = renderTimelineWithLeftAndRightSidebar()
     const headerContainer = getByTestId('headerContainer')
@@ -116,15 +130,16 @@ describe('TimelineHeader', () => {
     expect(getAllByTestId('sidebarHeader')).toHaveLength(1)
   })
   it('Given SidebarHeader When passing variant prop with right value Then it should rendered above the right sidebar', () => {
-    const { getByTestId, getAllByTestId, debug } = renderSidebarHeaderWithCustomValues(
-      { variant: 'right' }
-    )
+    const {
+      getByTestId,
+      getAllByTestId,
+      debug
+    } = renderSidebarHeaderWithCustomValues({ variant: 'right' })
     expect(getByTestId('sidebarHeader')).toBeInTheDocument()
     expect(getAllByTestId('sidebarHeader')).toHaveLength(2)
-    expect(getAllByTestId('sidebarHeader')[1].previousElementSibling).toHaveAttribute(
-      'data-testid',
-      'headerContainer'
-    )
+    expect(
+      getAllByTestId('sidebarHeader')[1].previousElementSibling
+    ).toHaveAttribute('data-testid', 'headerContainer')
   })
 
   it('Given SidebarHeader When passing variant prop with unusual value Then it should rendered above the left sidebar by default', () => {