Handle singular form of SIBLINGS action.

- Updated tests to handle `SIBLING` action
- Added assumptions to README

1 files changed, 3 insertions, 1 deletions

diff --git a/spec/family_tree_spec.rb b/spec/family_tree_spec.rb
index dcff803..0d7c101 100644
--- a/spec/family_tree_spec.rb
+++ b/spec/family_tree_spec.rb
@@ -67,10 +67,12 @@ RSpec.describe FamilyTree do
 
     context 'finding siblings' do
       it 'returns sibling\'s name if present' do
-        expect(FamilyTree.instance.get_relationship('Draco', 'siblings')).to eq('Aster')
+        expect(FamilyTree.instance.get_relationship('Draco', 'sibling')).to eq('Aster')
+        expect(FamilyTree.instance.get_relationship('Draco', 'sibling')).to eq('Aster')
       end
 
       it 'returns NONE if there are no siblings' do
+        expect(FamilyTree.instance.get_relationship('Remus', 'sibling')).to eq('NONE')
         expect(FamilyTree.instance.get_relationship('Remus', 'siblings')).to eq('NONE')
       end
     end