Add "exclude" method to UniqueGenerator (faker-ruby#1307)

README.md

@@ -203,6 +203,18 @@ Faker::Name.unique.clear # Clears used values for Faker::Name
 Faker::UniqueGenerator.clear # Clears used values for all generators
 ```
 
+You also can give some already used values to the unique generator if you have
+collisions with the generated data (i.e: using FactoryBot with random and
+manually set values).
+
+```ruby
+# Usage:
+# Faker::<generator>.unique.exclude(method, arguments, list)
+
+# Add 'azerty' and 'wxcvbn' to the string generator with 6 char length
+Faker::Lorem.unique.exclude :string, [6], %w[azerty wxcvbn]
+```
+
 ### Deterministic Random
 
 Faker supports seeding of its pseudo-random number generator (PRNG) to provide deterministic output of repeated method calls.

lib/helpers/unique_generator.rb

@@ -36,5 +36,12 @@ def clear
     def self.clear
       ObjectSpace.each_object(self, &:clear)
     end
+
+    def exclude(name, arguments, values)
+      values ||= []
+      values.each do |value|
+        @previous_results[[name, arguments]] << value
+      end
+    end
   end
 end

test/test_faker_lorem.rb

@@ -116,4 +116,10 @@ def test_paragraph_char_count
     paragraph = @tester.paragraph_by_chars(256)
     assert(paragraph.length == 256)
   end
+
+  def test_unique_with_already_set_values
+    values = ('a'..'z').to_a + ('0'..'9').to_a
+    @tester.unique.exclude(:character, [], values)
+    assert_raise(Faker::UniqueGenerator::RetryLimitExceeded) { @tester.unique.character }
+  end
 end