properly mock the environment where tested file is expected to run

lib/docker-sync/dependencies.rb

@@ -23,14 +23,7 @@ def self.ensure_all_for_mac!(config)
       Docker.ensure!
       Unison.ensure!  if config.unison_required?
       Rsync.ensure!   if config.rsync_required?
-      if config.fswatch_required?
-        unless Fswatch.available?
-          Fswatch.ensure!
-          puts "please restart docker sync so the installation of fswatch takes effect"
-          raise(UNSUPPORTED_OPERATING_SYSTEM)
-        end
-      end
-
+      Fswatch.ensure! if config.fswatch_required?
     end
 
     def self.ensure_all_for_linux!(_config)

lib/docker-sync/dependencies/fswatch.rb

@@ -8,9 +8,12 @@ def self.available?
       end
 
       def self.ensure!
-        raise 'Fswatch cannot be installed on other platforms then MacOS' unless Environment.mac?
-        PackageManager.install_package('fswatch') unless available?
-      end
+        return if available?
+
+        PackageManager.install_package('fswatch')
+        puts "please restart docker sync so the installation of fswatch takes effect"
+        exit(1)
+    end
     end
   end
 end

spec/helpers/command_mocking_helpers.rb

@@ -1,5 +1,5 @@
 module CommandExecutionMock
-  COMMAND_EXECUTORS = %i(system exec spawn `).freeze
+  COMMAND_EXECUTORS = %i(system exec exit spawn `).freeze
 
   def self.included(_base)
     define_custom_matchers

spec/lib/docker-sync/dependencies/fswatch_spec.rb

@@ -1,6 +1,11 @@
 require 'spec_helper'
 
 RSpec.describe DockerSync::Dependencies::Fswatch do
+  before do
+    allow(DockerSync::Environment).to receive(:mac?).and_return(true)
+    allow(described_class).to receive(:exit)
+  end
+
   it_behaves_like 'a dependency'
   it_behaves_like 'a binary-checking dependency', 'fswatch'
   it_behaves_like 'a binary-installing dependency', 'fswatch'

spec/lib/docker-sync/dependencies_spec.rb

@@ -2,14 +2,16 @@
 
 RSpec.describe DockerSync::Dependencies do
   let(:config) { double(:config, unison_required?: false, rsync_required?: false, fswatch_required?: false) }
+  let(:linux?) { false }
+  let(:mac?)   { false }
 
-  describe '.ensure_all!(config)' do
-    let(:mac?)   { false }
-    let(:linux?) { false }
+  before do
+    allow(DockerSync::Environment).to receive(:linux?).and_return(linux?)
+    allow(DockerSync::Environment).to receive(:mac?).and_return(mac?)
+  end
 
+  describe '.ensure_all!(config)' do
     before do
-      allow(DockerSync::Environment).to receive(:mac?).and_return(mac?)
-      allow(DockerSync::Environment).to receive(:linux?).and_return(linux?)
       allow(described_class).to receive(:ensure_all_for_mac!)
       allow(described_class).to receive(:ensure_all_for_linux!)
     end
@@ -42,6 +44,8 @@
   end
 
   describe '.ensure_all_for_linux!(_config)' do
+    let(:linux?) { true }
+
     before do
       allow(described_class::Docker).to receive(:ensure!)
     end
@@ -55,9 +59,10 @@
   end
 
   describe '.ensure_all_for_mac!(config)' do
+    let(:mac?) { true }
+
     before do
       allow(described_class::PackageManager).to receive(:ensure!)
-      #allow(DockerSync::Dependencies::Fswatch).to receive(:ensure!).and_return(true)
       allow(described_class::Docker).to receive(:ensure!)
     end