Handle backspace keys in filter mode

lib/log_bench/app/input_handler.rb

@@ -15,6 +15,8 @@ class InputHandler
       CTRL_L = 12         # Clear requests
       CTRL_R = 18         # Undo clear requests (restore)
       ESC = 27            # Escape
+      BACKSPACE_KEYS = [127, 8, KEY_BACKSPACE].freeze
+      EXIT_FILTER_MODE_KEYS = [27, 10, 13].freeze # Escape, Enter, Return
 
       # UI constants
       DEFAULT_VISIBLE_HEIGHT = 20
@@ -62,15 +64,15 @@ def filter_mode_active?
 
       def handle_filter_input(ch)
         case ch
-        when 10, 13, 27  # Enter, Return, Escape
+        when *EXIT_FILTER_MODE_KEYS
           state.exit_filter_mode
         when KEY_UP
           state.exit_filter_mode
           state.navigate_up
         when KEY_DOWN
           state.exit_filter_mode
           state.navigate_down
-        when 127, 8  # Backspace
+        when *BACKSPACE_KEYS
           state.backspace_filter
         else
           add_character_to_filter(ch)

test/test_input_handler_filter.rb

@@ -0,0 +1,31 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class TestInputHandlerFilter < Minitest::Test
+  def setup
+    @state = test_state
+    @state.switch_to_left_pane
+    @state.enter_filter_mode
+    @state.add_to_filter("ab")
+    @input_handler = LogBench::App::InputHandler.new(@state, Object.new)
+  end
+
+  def test_backspace_ascii_127_removes_character
+    @input_handler.send(:handle_filter_input, 127)
+
+    assert_equal "a", @state.main_filter.display_text
+  end
+
+  def test_backspace_ctrl_h_removes_character
+    @input_handler.send(:handle_filter_input, 8)
+
+    assert_equal "a", @state.main_filter.display_text
+  end
+
+  def test_backspace_key_backspace_removes_character
+    @input_handler.send(:handle_filter_input, Curses::KEY_BACKSPACE)
+
+    assert_equal "a", @state.main_filter.display_text
+  end
+end