Add spec tests for FDroid link inline macro

spec/fdroid_link_inline_macro_spec.rb

@@ -0,0 +1,37 @@
+# frozen_string_literal: true
+
+describe FDroidLinkInlineMacro do
+  it 'should create a FDroid link' do
+    input = 'fdroid:org.moire.ultrasonic[]'
+
+    expected = <<~RESULT
+      <a href="https://f-droid.org/en/packages/org.moire.ultrasonic">Ultrasonic</a>
+    RESULT
+
+    actual = (Asciidoctor.convert input).tr_s '\n', '\n'
+    (expect actual).to include expected.chomp
+  end
+
+  it 'should create a FDroid link with replaced caption' do
+    input = 'fdroid:org.moire.ultrasonic[a Subsonic client]'
+
+    expected = <<~RESULT
+      <a href="https://f-droid.org/en/packages/org.moire.ultrasonic">a Subsonic client</a>
+    RESULT
+
+    actual = (Asciidoctor.convert input).tr_s '\n', '\n'
+    (expect actual).to include expected.chomp
+  end
+
+  it 'should fail to create a link due to non-existent app' do
+    input = 'fdroid:com.example.NonExistentAppOrSomething[]'
+
+    expect { Asciidoctor.convert input }.to raise_error StandardError
+  end
+
+  it 'should fail to create a link due to non-existent app even with replaced caption' do
+    input = 'fdroid:com.example.NonExistentAppOrSomething[non-existent app]'
+
+    expect { Asciidoctor.convert input }.to raise_error StandardError
+  end
+end