GREG-261: Default country code can be blank in form

The default country code does not get set in the form automatically even though it looks like it is selected in the list.

frontend/src/routes/guest/register/steps/register.test.tsx

@@ -392,3 +392,63 @@ test('Guest allowed to proceed in wizard if data is valid', async () => {
 
   expect(nextHandler.mock.calls.length).toBe(1)
 })
+
+test('Default country code gets set in form values', async () => {
+  // This stores the data sent from the form when the user clicks submit
+  let guestRegisterData: GuestRegisterData | null = null
+  const nextHandler = (registerData: GuestRegisterData) => {
+    guestRegisterData = registerData
+
+  }
+
+  const allFeaturesOn = {
+    displayContactAtUnit: true,
+    displayComment: true,
+    displayContactAtUnitGuestInput: true,
+    showGenderFieldForGuest: true,
+  }
+
+  // Leave the mobile phone country code blank, it should
+  // be populated with a default value
+  const formData: GuestRegisterData = {
+    firstName: 'Test',
+    lastName: 'Test2',
+    mobilePhoneCountry: '',
+    mobilePhone: '97543992',
+    nationalIdNumber: '',
+    passportNumber: '12345678',
+    passportNationality: 'NO',
+    dateOfBirth: addYears(-20)(new Date()),
+    gender: 'male',
+  }
+
+  const testData = getEmptyGuestData()
+  testData.gender = 'male'
+  const submitMock = jest.fn()
+
+  // Need this to be able to call on the submit-method on the form
+  const reference = {
+    current: {
+      doSubmit: submitMock,
+    },
+  }
+
+  render(
+    <FeatureContext.Provider value={allFeaturesOn}>
+      <LocalizationProvider dateAdapter={AdapterDateFns}>
+        <GuestRegisterStep
+          nextHandler={nextHandler}
+          initialGuestData={testData}
+          registerData={formData}
+          ref={reference}
+        />
+      </LocalizationProvider>
+    </FeatureContext.Provider>,
+  )
+
+  expect(guestRegisterData).toBeNull()
+  await act(async () => reference.current?.doSubmit())
+  // Check that the mobile country has gotten the default value
+  // @ts-ignore
+  expect(guestRegisterData.mobilePhoneCountry).toEqual('NO')
+})