Add spec for util.cr

spec/util_spec.cr

@@ -0,0 +1,28 @@
+require "./spec_helper"
+
+describe "compare_alphanumerically" do
+	it "sorts filenames with leading zeros correctly" do
+		ary = ["010.jpg", "001.jpg", "002.png"]
+		ary.sort! {|a, b|
+			compare_alphanumerically a, b
+		}
+		ary.should eq ["001.jpg", "002.png", "010.jpg"]
+	end
+
+	it "sorts filenames without leading zeros correctly" do
+		ary = ["10.jpg", "1.jpg", "0.png", "0100.jpg"]
+		ary.sort! {|a, b|
+			compare_alphanumerically a, b
+		}
+		ary.should eq ["0.png", "1.jpg", "10.jpg", "0100.jpg"]
+	end
+
+	# https://ux.stackexchange.com/a/95441
+	it "sorts like the stack exchange post" do
+		ary = ["2", "12", "200000", "1000000", "a", "a12", "b2", "text2",
+		 "text2a", "text2a2", "text2a12", "text2ab", "text12", "text12a"]
+		ary.reverse.sort {|a, b|
+			compare_alphanumerically a, b
+		}.should eq ary
+	end
+end