Relocates _start_with? method to array.rb

lib/foobara/util/array.rb

@@ -36,5 +36,15 @@ def all_blank_or_false?(array)
         )
       end
     end
+
+    def start_with?(large_array, small_array)
+      return false unless large_array.size >= small_array.size
+
+      small_array.each.with_index do |item, index|
+        return false unless large_array[index] == item
+      end
+
+      true
+    end
   end
 end

spec/array_spec.rb

@@ -36,4 +36,50 @@
       it { is_expected.to be(true) }
     end
   end
+
+  describe ".start_with?" do
+    subject { described_class.start_with?(large_array, small_array) }
+
+    context "when size of large array is smaller than size of small array" do
+      let(:large_array) { [1, 2, 3] }
+      let(:small_array) { [1, 2, 3, 4, 5, 6, 7] }
+
+      it { is_expected.to be(false) }
+    end
+
+    context "when large array starts with elements from small array" do
+      let(:large_array) { [1, 2, 3, 4, 5, 6, 7] }
+      let(:small_array) { [1, 2, 3, 4] }
+
+      it { is_expected.to be(true) }
+    end
+
+    context "when elements in small array don't match those in large array" do
+      let(:large_array) { [1, 2, 3, 4, 5, 6, 7] }
+      let(:small_array) { [5, 6, 7, 8] }
+
+      it { is_expected.to be(false) }
+    end
+
+    context "when first elements in small array match those in the large array but last elements don't match" do
+      let(:large_array) { [1, 2, 3, 4, 5, 6, 7] }
+      let(:small_array) { [1, 2, 8, 9] }
+
+      it { is_expected.to be(false) }
+    end
+
+    context "when small array and large array are of the same size" do
+      let(:large_array) { [1, 2, 3, 4] }
+      let(:small_array) { [1, 2, 3, 4] }
+
+      it { is_expected.to be(true) }
+    end
+
+    context "when both arrays are empty" do
+      let(:large_array) { [] }
+      let(:small_array) { [] }
+
+      it { is_expected.to be(true) }
+    end
+  end
 end