fix: don't care about missing deltas

lib/rubocop/cop/rspec/rails/minitest_assertions.rb

@@ -124,12 +124,10 @@ class InDeltaAssertion < BasicAssertion
             ].freeze
 
             NODE_MATCHER_PATTERN = <<~PATTERN
-              (send nil? {:assert_in_delta :assert_not_in_delta :refute_in_delta} $_ $_ $!{sym str}? $_?)
+              (send nil? {:assert_in_delta :assert_not_in_delta :refute_in_delta} $_ $_ $_? $_?)
             PATTERN
 
             def self.match(expected, actual, delta, failure_message)
-              return nil if delta.empty? && !failure_message.empty?
-
               new(expected, actual, delta.first, failure_message.first)
             end
 

spec/rubocop/cop/rspec/rails/minitest_assertions_spec.rb

@@ -335,6 +335,18 @@
       RUBY
     end
 
+    it 'registers an offense when using `assert_in_delta` with ' \
+       'a missing delta' do
+      expect_offense(<<~RUBY)
+        assert_in_delta a, b, "whoops, we forgot about the actual delta!"
+        ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `expect(b).to be_within("whoops, we forgot about the actual delta!").of(a)`.
+      RUBY
+
+      expect_correction(<<~RUBY)
+        expect(b).to be_within("whoops, we forgot about the actual delta!").of(a)
+      RUBY
+    end
+
     it 'registers an offense when using `assert_in_delta` with ' \
        'multi-line arguments' do
       expect_offense(<<~RUBY)
@@ -384,12 +396,6 @@
         expect(b).not_to be_within(1).of(a)
       RUBY
     end
-
-    it 'does not register an offense when the delta is missing' do
-      expect_no_offenses(<<~RUBY)
-        assert_in_delta a, b, "whoops, we forgot about the actual delta!"
-      RUBY
-    end
   end
 
   context 'with match assertions' do