Match error class using case instead of if/elsif/else (#16952)

* prefer case to multiple if branches

case klass works fine on inheritance chains (we don't need to match on
inheritance explicitly).

* Verify case on error class behaves as before

* Fix tests

I don't know how I committed tests that were failing, but don't do that

app/services/twitter_client/client.rb

@@ -44,9 +44,10 @@ module TwitterClient
         error_class = "::TwitterClient::Errors::#{class_name}".safe_constantize
         raise error_class, exception.message if error_class
 
-        error_class = if exception.class < Twitter::Error::ClientError
+        error_class = case exception
+                      when Twitter::Error::ClientError
                         TwitterClient::Errors::ClientError
-                      elsif exception.class < Twitter::Error::ServerError
+                      when Twitter::Error::ServerError
                         TwitterClient::Errors::ServerError
                       else
                         TwitterClient::Errors::Error

spec/services/twitter_client/client_spec.rb

@@ -27,4 +27,36 @@ RSpec.describe TwitterClient::Client, type: :service, vcr: true do
       end
     end
   end
+
+  describe "handling underlying errors" do
+    let(:client) { instance_double(Twitter::REST::Client) }
+
+    before do
+      allow(Twitter::REST::Client).to receive(:new).and_return(client)
+    end
+
+    it "matches defined errors by name" do
+      allow(client).to receive(:status).and_raise(Twitter::Error::NotFound)
+
+      expect { described_class.status(1) }.to raise_error(TwitterClient::Errors::NotFound)
+    end
+
+    it "matches client errors" do
+      allow(client).to receive(:status).and_raise(Twitter::Error::BadRequest)
+
+      expect { described_class.status(1) }.to raise_error(TwitterClient::Errors::ClientError)
+    end
+
+    it "matches server errors" do
+      allow(client).to receive(:status).and_raise(Twitter::Error::ServiceUnavailable)
+
+      expect { described_class.status(1) }.to raise_error(TwitterClient::Errors::ServerError)
+    end
+
+    it "defaults to a generic error" do
+      allow(client).to receive(:status).and_raise(Twitter::Error)
+
+      expect { described_class.status(1) }.to raise_error(TwitterClient::Errors::Error)
+    end
+  end
 end