Provide better error messages

lib/administrate/not_authorized_error.rb

@@ -4,7 +4,15 @@ def initialize(action:, resource:)
       @action = action
       @resource = resource
 
-      super("not allowed to #{action.inspect} this #{resource.class}")
+      case resource
+      when Module, String, Symbol
+        super("Not allowed to perform #{action.inspect} on #{resource.inspect}")
+      else
+        super(
+          "Not allowed to perform #{action.inspect} on the given " +
+            resource.class.name
+        )
+      end
     end
   end
 end

spec/lib/administrate/not_authorized_error_spec.rb

@@ -0,0 +1,51 @@
+require "rails_helper"
+
+describe Administrate::NotAuthorizedError do
+  context "when the resource is a class or module" do
+    it "produces a message mentioning it directly" do
+      error = described_class.new(
+        resource: Administrate,
+        action: "foo",
+      )
+      expect(error.message).to eq(
+        %{Not allowed to perform "foo" on Administrate}
+      )
+    end
+  end
+
+  context "when the resource is a string" do
+    it "produces a message mentioning it directly" do
+      error = described_class.new(
+        resource: "User",
+        action: "foo",
+      )
+      expect(error.message).to eq(%{Not allowed to perform "foo" on "User"})
+    end
+  end
+
+  context "when the resource is a symbol" do
+    it "produces a message mentioning it directly" do
+      error = described_class.new(
+        resource: :user,
+        action: "foo",
+      )
+      expect(error.message).to eq(%{Not allowed to perform "foo" on :user})
+    end
+  end
+
+  context "when the resource is something else" do
+    it "produces a message that refers to the class of the resource" do
+      class TestStuff; end
+
+      error = described_class.new(
+        resource: TestStuff.new,
+        action: "foo",
+      )
+      expect(error.message).to eq(
+        %{Not allowed to perform "foo" on the given TestStuff}
+      )
+    ensure
+      remove_constants :TestStuff
+    end
+  end
+end