config: default options table with deep merge

tests/test_config.lua

@@ -0,0 +1,37 @@
+-- tests for config module
+local config = require("tiny-debugger.config")
+
+local function assert_eq(a, b, msg)
+  if a ~= b then
+    error(string.format("FAIL: %s — expected %s, got %s", msg, vim.inspect(b), vim.inspect(a)))
+  end
+end
+
+-- test 1: defaults unchanged after empty merge
+local opts = config.merge({})
+assert_eq(opts.keys.continue, "c", "default continue key")
+assert_eq(opts.help_on_enter, true, "default help_on_enter")
+assert_eq(opts.builtin_adapters, true, "default builtin_adapters")
+assert_eq(#opts.dapui.layouts, 2, "default layout count")
+
+-- test 2: partial key override
+opts = config.merge({ keys = { continue = "g" } })
+assert_eq(opts.keys.continue, "g", "overridden continue key")
+assert_eq(opts.keys.step_over, "s", "preserved step_over key")
+assert_eq(opts.keys.terminate, "q", "preserved terminate key")
+
+-- test 3: disable a key with false
+opts = config.merge({ keys = { continue = false } })
+assert_eq(opts.keys.continue, false, "disabled continue key")
+assert_eq(opts.keys.step_over, "s", "preserved step_over after disable")
+
+-- test 4: override help_on_enter
+opts = config.merge({ help_on_enter = false })
+assert_eq(opts.help_on_enter, false, "overridden help_on_enter")
+assert_eq(opts.keys.continue, "c", "keys preserved after help override")
+
+-- test 5: merge doesn't mutate defaults
+config.merge({ keys = { continue = "z" } })
+assert_eq(config.defaults.keys.continue, "c", "defaults not mutated")
+
+print("ALL CONFIG TESTS PASSED")