add tests for :instance and :exists

Signed-off-by: Chris Redekop <chris.redekop@d2l.com>

test/unit/resources/ec2_test.rb

@@ -14,14 +14,11 @@ class TestEc2 < Minitest::Test
     @mockConn.expect :ec2_resource, @mockResource
   end
 
-  def test_that_id_returns_directly_provided_id
-    @cut = Ec2.new(Id, @mockConn)
-     
-    assert_equal @cut.id, Id
+  def test_that_id_returns_id_directly_when_constructed_with_an_id
+    assert_equal Id, Ec2.new(Id, @mockConn).id
   end
 
-  def test_that_id_returns_id_for_provided_name
-    @cut = Ec2.new({name: 'cut'}, @mockConn)
+  def test_that_id_returns_fetched_id_when_constructed_with_a_name
     mockInstance = Minitest::Mock.new
 
     mockInstance.expect :nil?, false
@@ -29,6 +26,38 @@ class TestEc2 < Minitest::Test
 
     @mockResource.expect :instances, [mockInstance], [Hash]
      
-    assert_equal @cut.id, Id
+    assert_equal Id, Ec2.new({name: 'cut'}, @mockConn).id
   end
+
+  def test_that_instance_returns_instance_when_instance_exists
+    mockInstance = Object.new
+
+    @mockResource.expect :instance, mockInstance, [Id] 
+
+    assert_same mockInstance, Ec2.new(Id, @mockConn).send(:instance)
+  end
+
+  def test_that_instance_returns_nil_when_instance_does_not_exist
+    @mockResource.expect :instance, nil, [Id] 
+
+    assert Ec2.new(Id, @mockConn).send(:instance).nil?
+  end
+
+  def test_that_exists_returns_true_when_instance_exists
+    mockInstance = Object.new
+
+    @mockResource.expect :instance, mockInstance, [Id] 
+
+    assert Ec2.new(Id, @mockConn).exists?
+  end
+
+  # A test similar to this one should pass once issue #13 is fixed`
+  # def test_that_exists_returns_false_when_instance_does_not_exist
+    # @cut = Ec2.new(Id, @mockConn)
+    # mockInstance = Object.new
+
+    # @mockResource.expect :instance, nil, [Id] 
+
+    # assert_false @cut.exists?
+  # end
 end