diff --git a/Gemfile b/Gemfile
index 8e54876e..4f8e6681 100644
--- a/Gemfile
+++ b/Gemfile
@@ -2,7 +2,6 @@ source "https://rubygems.org"
 
 gemspec
 
-gem "ammeter", ">= 1.1.3"
 gem "bundler", ">= 1.5"
 gem "database_cleaner"
 gem "pg"
diff --git a/spec/generators/fx/function/function_generator_spec.rb b/spec/generators/fx/function/function_generator_spec.rb
index a9dfcdc9..92317e79 100644
--- a/spec/generators/fx/function/function_generator_spec.rb
+++ b/spec/generators/fx/function/function_generator_spec.rb
@@ -6,11 +6,11 @@
     migration = file("db/migrate/create_function_test.rb")
     function_definition = file("db/functions/test_v01.sql")
 
-    run_generator ["test"]
+    run_generator(described_class, ["test"])
 
     expect(function_definition).to exist
-    expect(migration).to be_a_migration
-    expect(migration_file(migration)).to contain("CreateFunctionTest")
+    expect_to_be_a_migration(migration)
+    expect(migration_content(migration)).to include("CreateFunctionTest")
   end
 
   context "when passed --no-migration" do
@@ -18,10 +18,10 @@
       migration = file("db/migrate/create_function_test.rb")
       function_definition = file("db/functions/test_v01.sql")
 
-      run_generator ["test", "--no-migration"]
+      run_generator(described_class, ["test"], {migration: false})
 
       expect(function_definition).to exist
-      expect(Pathname.new(migration_file(migration))).not_to exist
+      expect(migration).not_to exist
     end
   end
 
@@ -35,12 +35,11 @@
       migration = file("db/migrate/update_function_test_to_version_2.rb")
       function_definition = file("db/functions/test_v02.sql")
 
-      run_generator ["test"]
+      run_generator(described_class, ["test"])
 
       expect(function_definition).to exist
-      expect(migration).to be_a_migration
-      expect(migration_file(migration))
-        .to contain("UpdateFunctionTestToVersion2")
+      expect_to_be_a_migration(migration)
+      expect(migration_content(migration)).to include("UpdateFunctionTestToVersion2")
     end
   end
 end
diff --git a/spec/generators/fx/trigger/trigger_generator_spec.rb b/spec/generators/fx/trigger/trigger_generator_spec.rb
index b56305dc..e467968b 100644
--- a/spec/generators/fx/trigger/trigger_generator_spec.rb
+++ b/spec/generators/fx/trigger/trigger_generator_spec.rb
@@ -6,12 +6,15 @@
     migration = file("db/migrate/create_trigger_test.rb")
     trigger_definition = file("db/triggers/test_v01.sql")
 
-    run_generator ["test", "table_name" => "some_table"]
+    run_generator(
+      described_class,
+      ["test", {"table_name" => "some_table"}]
+    )
 
     expect(trigger_definition).to exist
-    expect(migration).to be_a_migration
-    expect(migration_file(migration)).to contain("CreateTriggerTest")
-    expect(migration_file(migration)).to contain("on: :some_table")
+    expect_to_be_a_migration(migration)
+    expect(migration_content(migration)).to include("CreateTriggerTest")
+    expect(migration_content(migration)).to include("on: :some_table")
   end
 
   context "when passed --no-migration" do
@@ -19,10 +22,14 @@
       migration = file("db/migrate/create_trigger_test.rb")
       trigger_definition = file("db/triggers/test_v01.sql")
 
-      run_generator ["test", {"table_name" => "some_table"}, "--no-migration"]
+      run_generator(
+        described_class,
+        ["test", {"table_name" => "some_table"}],
+        {migration: false}
+      )
 
       expect(trigger_definition).to exist
-      expect(Pathname.new(migration_file(migration))).not_to exist
+      expect(migration).not_to exist
     end
   end
 
@@ -30,17 +37,23 @@
     migration = file("db/migrate/create_trigger_test.rb")
     trigger_definition = file("db/triggers/test_v01.sql")
 
-    run_generator ["test", "on" => "some_table"]
+    run_generator(
+      described_class,
+      ["test", {"on" => "some_table"}]
+    )
 
     expect(trigger_definition).to exist
-    expect(migration).to be_a_migration
-    expect(migration_file(migration)).to contain("CreateTriggerTest")
-    expect(migration_file(migration)).to contain("on: :some_table")
+    expect_to_be_a_migration(migration)
+    expect(migration_content(migration)).to include("CreateTriggerTest")
+    expect(migration_content(migration)).to include("on: :some_table")
   end
 
   it "requires `table_name` or `on` to be specified" do
     expect do
-      run_generator ["test", "foo" => "some_table"]
+      run_generator(
+        described_class,
+        ["test", {"foo" => "some_table"}]
+      )
     end.to raise_error(ArgumentError)
   end
 
@@ -49,11 +62,14 @@
     migration = file("db/migrate/update_trigger_test_to_version_2.rb")
     trigger_definition = file("db/triggers/test_v02.sql")
 
-    run_generator ["test", "table_name" => "some_table"]
+    run_generator(
+      described_class,
+      ["test", {"table_name" => "some_table"}]
+    )
 
     expect(trigger_definition).to exist
-    expect(migration).to be_a_migration
-    expect(migration_file(migration)).to contain("UpdateTriggerTestToVersion2")
-    expect(migration_file(migration)).to contain("on: :some_table")
+    expect_to_be_a_migration(migration)
+    expect(migration_content(migration)).to include("UpdateTriggerTestToVersion2")
+    expect(migration_content(migration)).to include("on: :some_table")
   end
 end
diff --git a/spec/support/generator_setup.rb b/spec/support/generator_setup.rb
index 6ef9b0df..a8d425fa 100644
--- a/spec/support/generator_setup.rb
+++ b/spec/support/generator_setup.rb
@@ -1,11 +1,52 @@
-require "ammeter/init"
+module GeneratorSetup
+  RAILS_ROOT = Pathname.new(File.expand_path("../../../tmp/dummy", __dir__)).freeze
+  MIGRATION_TIMESTAMP_PATTERN = /\A\d{14}_/
+
+  def run_generator(generator_class, args = [], options = {})
+    allow(Rails).to receive(:root).and_return(RAILS_ROOT)
+    generator = generator_class.new(args, options, destination_root: RAILS_ROOT)
+
+    silence_stream($stdout) do
+      generator.invoke_all
+    end
+  end
+
+  def file(relative_path)
+    RAILS_ROOT.join(relative_path)
+  end
+
+  def migration_content(file_path)
+    migration_path = find_migration_files(file_path).first
+    return if migration_path.nil?
+
+    Pathname.new(migration_path).read
+  end
+
+  def find_migration_files(file_path)
+    directory = File.dirname(file_path)
+    basename = File.basename(file_path, ".rb")
+    Dir.glob(File.join(directory, "*#{basename}.rb"))
+  end
+
+  def expect_to_be_a_migration(pathname)
+    migration_files = find_migration_files(pathname)
+
+    expect(migration_files).to be_present,
+      "expected #{pathname} to be a migration file"
+    first_migration = migration_files.first
+    migration_basename = File.basename(first_migration)
+    expect(migration_basename).to match(MIGRATION_TIMESTAMP_PATTERN),
+      "expected #{migration_basename} to have timestamp prefix (format: YYYYMMDDHHMMSS_)"
+  end
+end
 
 RSpec.configure do |config|
+  config.include GeneratorSetup, :generator
+
   config.before(:each, :generator) do
-    fake_rails_root = File.expand_path("../../../tmp/dummy", __FILE__)
-    allow(Rails).to receive(:root).and_return(Pathname.new(fake_rails_root))
+    FileUtils.rm_rf(GeneratorSetup::RAILS_ROOT) if File.exist?(GeneratorSetup::RAILS_ROOT)
+    FileUtils.mkdir_p(GeneratorSetup::RAILS_ROOT)
 
-    destination fake_rails_root
-    prepare_destination
+    allow(Rails).to receive(:root).and_return(Pathname.new(GeneratorSetup::RAILS_ROOT))
   end
 end