Add test range param to NHS numbers

doc/default/national_health_service.md

@@ -1,8 +1,9 @@
 # Faker::NationalHealthService
 
-```ruby
-Faker::NationalHealthService.british_number #=> "403 958 5577"
+The NHS sets aside a range of numbers from 999 000 0000 to 999 999 9999 for
+test purposes. For more details, see [NHS Digital documentation about
+synthetic data](https://digital.nhs.uk/services/e-referral-service/document-library/synthetic-data-in-live-environments#synthetic-data-naming-convention).
 
-# Keyword arguments: number
-Faker::NationalHealthService.check_digit(number: 400_012_114) #=> 6
+```ruby
+Faker::NationalHealthService.british_number #=> "999 464 0232"
 ```

lib/faker/default/national_health_service.rb

@@ -6,14 +6,17 @@ class << self
       ##
       # Produces a random British NHS number.
       #
+      # The NHS sets aside a range of numbers from 999 000 0000 to 999 999 9999
+      # for test purposes.
+      #
       # @return [String]
       #
       # @example
-      #   Faker::NationalHealthService.british_number #=> "403 958 5577"
+      #   Faker::NationalHealthService.british_number #=> "999 464 0232"
       #
       # @faker.version 1.9.2
       def british_number
-        base_number = rand(400_000_001...499_999_999)
+        base_number = rand(999_000_001...999_999_999)
         # If the check digit is equivalent to 10, the number is invalid.
         # See https://en.wikipedia.org/wiki/NHS_number
         base_number -= 1 if check_digit(number: base_number) == 10
@@ -24,6 +27,8 @@ def british_number
                                                            .join
       end
 
+      private
+
       ##
       # Produces a random British NHS number's check digit.
       #

test/faker/default/test_faker_national_health_service.rb

@@ -8,20 +8,12 @@ def setup
   end
 
   def test_nhs_british_number
-    assert_match(/\A\d{3}\s\d{3}\s\d{4}\z/, @tester.british_number)
+    assert_match(/\A9{3}\s\d{3}\s\d{4}\z/, @tester.british_number)
   end
 
   def test_check_digit_equals_10
-    Faker::NationalHealthService.stub(:rand, 458_617_434) do
-      assert_match('458 617 4331', @tester.british_number)
+    Faker::NationalHealthService.stub(:rand, 999_464_033) do
+      assert_match('999 464 0321', @tester.british_number)
     end
   end
-
-  def test_check_digit
-    assert_equal 6, @tester.check_digit(number: 400_012_114)
-  end
-
-  def test_check_digit_11
-    assert_equal 0, @tester.check_digit(number: 418_513_625)
-  end
 end