Use stubbed certificate and key in Helm factory

spec/factories/clusters/applications/helm.rb

@@ -4,6 +4,20 @@ FactoryBot.define do
   factory :clusters_applications_helm, class: Clusters::Applications::Helm do
     cluster factory: %i(cluster provided_by_gcp)
 
+    before(:create) do
+      allow(Gitlab::Kubernetes::Helm::Certificate).to receive(:generate_root)
+        .and_return(
+          double(
+            key_string: File.read(Rails.root.join('spec/fixtures/clusters/sample_key.key')),
+            cert_string: File.read(Rails.root.join('spec/fixtures/clusters/sample_cert.pem'))
+          )
+        )
+    end
+
+    after(:create) do
+      allow(Gitlab::Kubernetes::Helm::Certificate).to receive(:generate_root).and_call_original
+    end
+
     trait :not_installable do
       status(-2)
     end

spec/fixtures/clusters/sample_key.key

@@ -0,0 +1,9 @@
+-----BEGIN RSA PRIVATE KEY-----
+MIIBOgIBAAJBAMA5sXIBE0HwgIB40iNidN4PGWzOyLQK0bsdOBNgpEXkDlZBvnak
+OUgAPF+rME4PB0Yl415DabUI40T5UNmlwxcCAwEAAQJAZtY2pSwIFm3JAXIh0cZZ
+iXcAfiJ+YzuqinUOS+eW2sBCAEzjcARlU/o6sFQgtsOi4FOMczAd1Yx8UDMXMmrw
+2QIhAPBgVhJiTF09pdmeFWutCvTJDlFFAQNbrbo2X2x/9WF9AiEAzLgqMKeStSRu
+H9N16TuDrUoO8R+DPqriCwkKrSHaWyMCIFzMhE4inuKcSywBaLmiG4m3GQzs++Al
+A6PRG/PSTpQtAiBxtBg6zdf+JC3GH3zt/dA0/10tL4OF2wORfYQghRzyYQIhAL2l
+0ZQW+yLIZAGrdBFWYEAa52GZosncmzBNlsoTgwE4
+-----END RSA PRIVATE KEY-----