1 files changed, 39 insertions, 0 deletions
diff --git a/CLI/ruby/spec/plane_spec.rb b/CLI/ruby/spec/plane_spec.rb
new file mode 100644
index 0000000..c4efbb4
--- /dev/null
+++ b/CLI/ruby/spec/plane_spec.rb
@@ -0,0 +1,39 @@
+# frozen_string_literal: true
+
+RSpec.describe GameOfLife::Plane do
+  describe "#[]" do
+    context "when empty" do
+      subject { described_class.new }
+
+      it "returns nil with [-1]" do
+        expect(subject[-1]).to be_nil
+      end
+
+      it "returns nil with [0]" do
+        expect(subject[0]).to be_nil
+      end
+
+      it "returns nil with [1]" do
+        expect(subject[1]).to be_nil
+      end
+    end
+
+    context "when not empty" do
+      subject { described_class.new([0, 1, 2, 3]) }
+
+      it "returns value at index" do
+        expect(subject[0]).to eq 0
+      end
+
+      it "returns value at -index (negative indices count backward from the end of the array)" do
+        expect(subject[-5]).to eq 3
+        expect(subject[-1]).to eq 3
+      end
+
+      it "returns value at any index (indices bigger than size cycle again from the beginning)" do
+        expect(subject[5]).to eq 1
+        expect(subject[9]).to eq 1
+      end
+    end
+  end
+end