diff --git a/test/models/registrant_user_test.rb b/test/models/registrant_user_test.rb
new file mode 100644
index 000000000..112b4dbeb
--- /dev/null
+++ b/test/models/registrant_user_test.rb
@@ -0,0 +1,49 @@
+class RegistrantUserTest < ActiveSupport::TestCase
+  def setup
+    super
+  end
+
+  def teardown
+    super
+  end
+
+  def test_find_or_create_by_api_data_creates_a_user
+    user_data = {
+      ident: '37710100070',
+      first_name: 'JOHN',
+      last_name: 'SMITH'
+    }
+
+    RegistrantUser.find_or_create_by_api_data(user_data)
+
+    user = User.find_by(registrant_ident: 'EE-37710100070')
+    assert_equal('JOHN SMITH', user.username)
+  end
+
+  def test_find_or_create_by_mid_data_creates_a_user
+    user_data = OpenStruct.new(user_country: 'EE', user_id_code: '37710100070',
+                              user_givenname: 'JOHN', user_surname: 'SMITH')
+
+    RegistrantUser.find_or_create_by_mid_data(user_data)
+    user = User.find_by(registrant_ident: 'EE-37710100070')
+    assert_equal('JOHN SMITH', user.username)
+  end
+
+  def test_find_or_create_by_idc_with_legacy_header_creates_a_user
+    header = '/C=EE/O=ESTEID/OU=authentication/CN=SMITH,JOHN,37710100070/SN=SMITH/GN=JOHN/serialNumber=37710100070'
+
+    RegistrantUser.find_or_create_by_idc_data(header, RegistrantUser::ACCEPTED_ISSUER)
+
+    user = User.find_by(registrant_ident: 'EE-37710100070')
+    assert_equal('JOHN SMITH', user.username)
+  end
+
+  def test_find_or_create_by_idc_with_rfc2253_header_creates_a_user
+    header = 'serialNumber=37710100070,GN=JOHN,SN=SMITH,CN=SMITH\\,JOHN\\,37710100070,OU=authentication,O=ESTEID,C=EE'
+
+    RegistrantUser.find_or_create_by_idc_data(header, RegistrantUser::ACCEPTED_ISSUER)
+
+    user = User.find_by(registrant_ident: 'EE-37710100070')
+    assert_equal('JOHN SMITH', user.username)
+  end
+end