Add spec tests for man inline macro

spec/man_inline_macro_spec.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+describe ManInlineMacro do
+  it 'should process with the default manpage service' do
+    input = 'man:ls[1]'
+
+    expected = <<~RESULT
+      <a href="https://manpages.debian.org/ls.1">ls(1)</a>
+    RESULT
+
+    actual = (Asciidoctor.convert input).tr_s '\n', '\n'
+    (expect actual).to include expected.chomp
+  end
+
+  it 'should link to the Arch Linux manpage' do
+    input = 'man:ls[volnum=1, service=arch]'
+
+    expected = <<~RESULT
+      <a href="https://man.archlinux.org/man/ls.1">ls(1)</a>
+    RESULT
+
+    actual = (Asciidoctor.convert input).tr_s '\n', '\n'
+    (expect actual).to include expected.chomp
+  end
+
+  it 'should link to the empty service' do
+    input = 'man:ls[volnum=1, service=none]'
+
+    expected = '<p>ls(1)</p>'
+
+    actual = (Asciidoctor.convert input).tr_s '\n', '\n'
+    (expect actual).to include expected
+  end
+
+  it 'should raise an error from non-existent service type' do
+    input = 'man:ls[volnum=1, service=manpageservicexyz]'
+
+    expect { Asciidoctor.convert input }.to raise_error StandardError
+  end
+end