1 files changed, 31 insertions, 0 deletions
diff --git a/spec/lib/banzai/filter/truncate_source_filter_spec.rb b/spec/lib/banzai/filter/truncate_source_filter_spec.rb
new file mode 100644
index 00000000000..b0c6d91daa8
--- /dev/null
+++ b/spec/lib/banzai/filter/truncate_source_filter_spec.rb
@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe Banzai::Filter::TruncateSourceFilter do
+  include FilterSpecHelper
+
+  let(:short_text) { 'foo' * 10 }
+  let(:long_text) { ([short_text] * 10).join(' ') }
+
+  it 'does nothing when limit is unspecified' do
+    output = filter(long_text)
+
+    expect(output).to eq(long_text)
+  end
+
+  it 'does nothing to a short-enough text' do
+    output = filter(short_text, limit: short_text.bytesize)
+
+    expect(output).to eq(short_text)
+  end
+
+  it 'truncates UTF-8 text by bytes, on a character boundary' do
+    utf8_text = '日本語の文字が大きい'
+    truncated = '日…'
+
+    expect(filter(utf8_text, limit: truncated.bytesize)).to eq(truncated)
+    expect(filter(utf8_text, limit: utf8_text.bytesize)).to eq(utf8_text)
+    expect(filter(utf8_text, limit: utf8_text.mb_chars.size)).not_to eq(utf8_text)
+  end
+end