Delete Tests

test_database.rb

...
  
  def test_delete_happy_path
    db = Database.new

    db.set "Tufted", "Titmouse"
    assert_equal("Titmouse", db.get("Tufted"))

    db.delete "Tufted"
    assert_equal("NULL", db.get("Tufted"))
  end

  def test_delete_absent_key
    db = Database.new

    assert_equal("That key isn't in the database!", db.delete("NoKey"))
  end
  
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