Add basic coverage for MuteWorker job (#39384)

spec/workers/mute_worker_spec.rb

@@ -0,0 +1,44 @@
+# frozen_string_literal: true
+
+require 'rails_helper'
+
+RSpec.describe MuteWorker do
+  let(:worker) { described_class.new }
+
+  describe '#perform' do
+    subject { worker.perform(account_id, target_account_id) }
+
+    let(:account) { Fabricate :account }
+    let(:target_account) { Fabricate :account }
+
+    let(:account_id) { account.id }
+    let(:target_account_id) { target_account.id }
+
+    context 'when account is invalid' do
+      let(:account_id) { nil }
+
+      it { is_expected.to be(true) }
+    end
+
+    context 'when target account is invalid' do
+      let(:target_account_id) { nil }
+
+      it { is_expected.to be(true) }
+    end
+
+    context 'with feed contents' do
+      let(:manager_service) { instance_double(FeedManager, clear_from_home: nil, clear_from_lists: nil) }
+
+      before { allow(FeedManager).to receive(:instance).and_return manager_service }
+
+      it 'clears feeds' do
+        subject
+
+        expect(manager_service)
+          .to have_received(:clear_from_home).with(account, target_account)
+        expect(manager_service)
+          .to have_received(:clear_from_lists).with(account, target_account)
+      end
+    end
+  end
+end