Expand test hook to return empty output if line #clear is in input + write spec for test hook.

spec/test_hook.rb

@@ -1,6 +1,12 @@
 #!/usr/bin/env ruby
 # frozen_string_literal: true
 
+output = []
 $stdin.readlines.each do |line|
-  puts line.gsub(/([^\s]*)\s*=\s*(.*)/, '\1 = \2')
+  exit 0 if line.chomp == '#clear'
+  output << line.gsub(/([^\s]*)\s*=\s*(.*)/, '\1 = \2')
+end
+
+output.each do |line|
+  puts line
 end

spec/test_hook_spec.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+describe 'Test Hook' do
+  it 'adds spaces around =' do
+    out = run 'a=b'
+
+    expect(out).to eq('a = b')
+  end
+
+  it 'returns empty output if it as a #clear line' do
+    out = run "a=b\n#clear\nc = d"
+    expect(out).to eq ''
+  end
+
+  def run(input)
+    IO.popen ['ruby', "#{__dir__}/test_hook.rb"], mode: File::RDWR do |io|
+      io.write input
+      io.close_write
+      io.read.chomp
+    end
+  end
+end