Added a few tests

spec/openurl_spec.cr

@@ -1 +1,33 @@
+require "yaml"
 require "./spec_helper"
+require "../src/rules"
+
+describe "find_command" do
+  it "does not find a command on an empty config" do
+    Rules.find_command("https://duckduckgo.com", YAML.parse("")).should be_nil
+  end
+
+  it "can find a command with from a regex rule" do
+    Rules.find_command(
+      "https://duckduckgo.com",
+      YAML.parse [{"domain" => "duckduckgo.com", "command" => "a"}].to_yaml
+    ).should eq "a"
+  end
+
+  it "prioritizes subrules over rules" do
+    Rules.find_command(
+      "https://duckduckgo.com",
+      YAML.parse [{"protocol" => "https",
+                   "command" => "a",
+                   "subrules" => [{"domain" => "duckduckgo.com", "command" => "b"}]
+    }].to_yaml
+    ).should eq "b"
+  end
+
+  it "does not crash when no program is found" do
+    Rules.find_command(
+      "https://duckduckgo.com",
+      YAML.parse [{"protocol" => "magnet", "command" => "a"}].to_yaml
+    ).should be_nil
+  end
+end

src/rules.cr

@@ -37,7 +37,10 @@ module Rules
   end
 
   # Finds a command in the rules which the url matches
-  def find_command(url : String, config)
+  def find_command(url : String, config : YAML::Any)
+    if !config.as_a?
+      return nil
+    end
     config.as_a.each do |c|
       if test_rule(url, c)
         if c["subrules"]?