Rewrite specs (#13)

The current specs are not exhaustive, failing to find a number of bugs
in the gem.

Rewrite the specs to:

* test individual units rather than the gem as a whole at a high level

* clean up after themselves as much as possible

* have all data and setup for the specs in the spec files themselves

* test more scenarios

* draw attention to existing bugs that we're not fixing yet

* provide a more reliable basis to ensure the correct behaviour of
  future refactors

This commit also removes an unused private method from
Sinject::Container, discovered when it showed as uncovered in the spec
coverage report.

Co-authored-by: Tim Regener <Tim.Regener@sage.com>

lib/sinject/container.rb

@@ -167,12 +167,6 @@ def match?(contract, dependency)
       return false
     end
 
-    # this method is called to get a standard param type for comparison purposes
-    def param_type(type)
-      return :arg if type == :opt || type == :req
-      return :key if type == :keyreq || type == :key
-    end
-
     def create_instance(item)
       # check if a custom initializer block has been specified
       if item.initialize_block != nil

spec/sinject/class_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+require 'sinject/container_item'
+require 'sinject/container'
+require 'sinject/class'
+
+describe Class do
+  before { @original_container = Sinject::Container.instance }
+  after { Sinject::Container.instance = @original_container }
+
+  describe '.dependency' do
+    let(:container) { Sinject::Container.new }
+    let(:foo) { Class.new }
+    let(:bar) { Class.new }
+
+    before do
+      container.register(key: :foo, class: foo)
+      container.register(key: :bar, class: bar)
+    end
+
+    describe 'creates instance methods that' do
+      it 'have the names specified' do
+        expect(subject.instance_methods).not_to include(:foo, :bar)
+        subject.dependency :foo, :bar
+        expect(subject.instance_methods).to include(:foo, :bar)
+      end
+
+      it 'return the dependency registered with the same name in the container' do
+        subject.dependency :foo, :bar
+        instance = subject.new
+        expect(instance.foo).to be_an_instance_of(foo)
+        expect(instance.bar).to be_an_instance_of(bar)
+      end
+    end
+  end
+end