1 files changed, 140 insertions, 0 deletions
diff --git a/spec/lib/banzai/filter/front_matter_filter_spec.rb b/spec/lib/banzai/filter/front_matter_filter_spec.rb
new file mode 100644
index 00000000000..3071dc7cf21
--- /dev/null
+++ b/spec/lib/banzai/filter/front_matter_filter_spec.rb
@@ -0,0 +1,140 @@
+require 'rails_helper'
+
+describe Banzai::Filter::FrontMatterFilter do
+  include FilterSpecHelper
+
+  it 'allows for `encoding:` before the front matter' do
+    content = <<~MD
+      # encoding: UTF-8
+      ---
+      foo: foo
+      bar: bar
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    expect(output).not_to match 'encoding'
+  end
+
+  it 'converts YAML front matter to a fenced code block' do
+    content = <<~MD
+      ---
+      foo: :foo_symbol
+      bar: :bar_symbol
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include '---'
+      expect(output).to include "```yaml\nfoo: :foo_symbol\n"
+    end
+  end
+
+  it 'converts TOML frontmatter to a fenced code block' do
+    content = <<~MD
+      +++
+      foo = :foo_symbol
+      bar = :bar_symbol
+      +++
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include '+++'
+      expect(output).to include "```toml\nfoo = :foo_symbol\n"
+    end
+  end
+
+  it 'converts JSON front matter to a fenced code block' do
+    content = <<~MD
+      ;;;
+      {
+        "foo": ":foo_symbol",
+        "bar": ":bar_symbol"
+      }
+      ;;;
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include ';;;'
+      expect(output).to include "```json\n{\n  \"foo\": \":foo_symbol\",\n"
+    end
+  end
+
+  it 'converts arbitrary front matter to a fenced code block' do
+    content = <<~MD
+      ---arbitrary
+      foo = :foo_symbol
+      bar = :bar_symbol
+      ---
+
+      # Header
+
+      Content
+    MD
+
+    output = filter(content)
+
+    aggregate_failures do
+      expect(output).not_to include '---arbitrary'
+      expect(output).to include "```arbitrary\nfoo = :foo_symbol\n"
+    end
+  end
+
+  context 'on content without front matter' do
+    it 'returns the content unmodified' do
+      content = <<~MD
+        # This is some Markdown
+
+        It has no YAML front matter to parse.
+      MD
+
+      expect(filter(content)).to eq content
+    end
+  end
+
+  context 'on front matter without content' do
+    it 'converts YAML front matter to a fenced code block' do
+      content = <<~MD
+        ---
+        foo: :foo_symbol
+        bar: :bar_symbol
+        ---
+      MD
+
+      output = filter(content)
+
+      aggregate_failures do
+        expect(output).to eq <<~MD
+          ```yaml
+          foo: :foo_symbol
+          bar: :bar_symbol
+          ```
+
+        MD
+      end
+    end
+  end
+end