diff --git a/lib/trailblazer/test/operation/helper.rb b/lib/trailblazer/test/operation/helper.rb
index 0fbbd2d..b372778 100644
--- a/lib/trailblazer/test/operation/helper.rb
+++ b/lib/trailblazer/test/operation/helper.rb
@@ -8,20 +8,20 @@ def factory(operation_class, **args, &block)
       call!(operation_class, args.merge(raise_on_failure: true), &block)
     end
 
-    def mock_step(operation_class, id:, subprocess: nil, subprocess_path: nil)
-      raise ArgumentError, "Missing block: `mock_step` requires a block." unless block_given?
+    def mock_step(operation_class, id:, subprocess: nil, subprocess_path: nil, &block)
+      raise ArgumentError, "Missing block: `mock_step` requires a block." if block.nil?
 
-      block = ->(ctx, **) { yield(ctx) }
+      override = ->(*) { step block, replace: id, id: id }
 
-      # If deeply nested step needs to be mocked, use the `patch` provided by Subprocess
+      return Class.new(operation_class, &override) if subprocess_path.nil?
+
+      # Remove below check in 1.0.0
       if subprocess
-        return Class.new(operation_class) do
-          patch = { subprocess_path => ->() { step block, replace: id, id: id } }
-          step Subprocess(subprocess, patch: patch), replace: subprocess, id: subprocess
-        end
+        subprocess_path = [subprocess, *subprocess_path]
+        Trailblazer::Activity::Deprecate.warn caller_locations[0], ":subprocess is deprecated and will be removed in 1.0.0. Pass `subprocess_path: #{subprocess_path}` instead."
       end
 
-      Class.new(operation_class) { step block, replace: id, id: id }
+      Trailblazer::Activity::DSL::Linear::Patch.call(operation_class, subprocess_path, override)
     end
 
     # @private
diff --git a/test/docs/helpers/mocking_test.rb b/test/docs/helpers/mocking_test.rb
index ad55cf0..f416d6b 100644
--- a/test/docs/helpers/mocking_test.rb
+++ b/test/docs/helpers/mocking_test.rb
@@ -1,10 +1,16 @@
 require "test_helper"
 
-class DocsMockingTest < MiniTest::Spec
+class DocsMockingTest < Minitest::Spec
+  include Trailblazer::Test::Assertions
+  include Trailblazer::Test::Operation::Assertions
+  include Trailblazer::Test::Operation::Helper
+
+  User = Struct.new(:name)
+
   #:mock-show-operation
-  class Show < Trailblazer::Activity::FastTrack
-    class Complexity < Trailblazer::Activity::FastTrack
-      class ExternalApi < Trailblazer::Activity::FastTrack
+  class Show < Trailblazer::Operation
+    class Complexity < Trailblazer::Operation
+      class ExternalApi < Trailblazer::Operation
         step :make_call
         #~method
         include Testing.def_steps(:make_call)
@@ -26,19 +32,18 @@ class ExternalApi < Trailblazer::Activity::FastTrack
   end
   #:mock-show-operation end
 
-  include Trailblazer::Test::Operation::Helper
-
   describe "#mock_step" do
-    let(:default_params) { { seq: [] } }
+    let(:operation) { Show }
+    let(:default_ctx) { { seq: [] } }
     let(:expected_attrs) { {} }
 
     #:simple-mock-step
     it "mocks loading user" do
       new_activity = mock_step(Show, id: :load_user) do |ctx|
-        ctx[:user] = Struct.new(:name).new('Mocky')
+        ctx[:user] = User.new('Mocky')
       end
 
-      assert_pass new_activity, default_params, {} do |(signal, (ctx, flow_options))|
+      assert_pass({}, {}, operation: new_activity) do |ctx|
         assert_equal ctx[:user].name, 'Mocky'
 
         #~method
@@ -56,7 +61,7 @@ class ExternalApi < Trailblazer::Activity::FastTrack
       #:mock-subprocess end
 
       #~method
-      assert_pass new_activity, default_params, {} do |(signal, (ctx, flow_options))|
+      assert_pass({}, {}, operation: new_activity) do |ctx|
         assert_equal ctx[:seq], [:load_user]
       end
       #~method end
@@ -64,14 +69,14 @@ class ExternalApi < Trailblazer::Activity::FastTrack
 
     it "mocks subprocess step" do
       #:mock-subprocess-step
-      new_activity = mock_step(Show, id: :some_complex_task, subprocess: Show::Complexity) do
+      new_activity = mock_step(Show, id: :some_complex_task, subprocess_path: [Show::Complexity]) do
         # Mock only single step from nested activity to do nothing
         true
       end
       #:mock-subprocess-step end
 
       #~method
-      assert_pass new_activity, default_params, {} do |(signal, (ctx, flow_options))|
+      assert_pass({}, {}, operation: new_activity) do |ctx|
         assert_equal ctx[:seq], [:load_user, :make_call]
       end
       #~method end
@@ -79,16 +84,33 @@ class ExternalApi < Trailblazer::Activity::FastTrack
 
     it "mocks nested subprocess step" do
       #:mock-nested-subprocess-step
-      new_activity = mock_step(Show, id: :make_call, subprocess: Show::Complexity, subprocess_path: [Show::Complexity::ExternalApi]) do
+      new_activity = mock_step(Show, id: :make_call, subprocess_path: [Show::Complexity, Show::Complexity::ExternalApi]) do
         # Some JSON response
+        { name: 'Mocky' }
       end
       #:mock-nested-subprocess-step end
 
       #~method
-      assert_pass new_activity, default_params, {} do |(signal, (ctx, flow_options))|
+      assert_pass({}, {}, operation: new_activity) do |ctx|
         assert_equal ctx[:seq], [:load_user, :some_complex_task]
       end
       #~method end
     end
+
+    it "shows warning for deprecated `subprocess`" do
+      #~method
+      _, warning = capture_io do
+        new_activity = mock_step(Show, id: :make_call, subprocess: Show::Complexity, subprocess_path: [Show::Complexity::ExternalApi]) do
+          { name: 'Mocky' }
+        end
+
+        assert_pass({}, {}, operation: new_activity) do |ctx|
+          assert_equal ctx[:seq], [:load_user, :some_complex_task]
+        end
+      end
+
+      assert_match ":subprocess is deprecated and will be removed in 1.0.0. Pass `subprocess_path: #{[Show::Complexity, Show::Complexity::ExternalApi]}` instead.", warning
+      #~method end
+    end
   end
 end