test: add comprehensive tests for Caddy.Server and Config validation

- Add server_test.exs with 10 passing tests
- Test configuration retrieval and updates
- Test binary path validation
- Test global and site configuration management
- Test path management and validation
- Fix unused variable warning in Server.bootstrap/0
- Improve test coverage for server lifecycle and configuration

Author: GSMLG-BOT

lib/caddy/server.ex

@@ -151,7 +151,7 @@ defmodule Caddy.Server do
 
         {:error, reason}
 
-      {:error, reason} = error ->
+      {:error, reason} ->
         duration = System.monotonic_time() - start_time
 
         Caddy.Telemetry.emit_server_event(:bootstrap_error, %{duration: duration}, %{

test/caddy/server_test.exs

@@ -0,0 +1,120 @@
+defmodule Caddy.ServerTest do
+  use ExUnit.Case, async: false
+
+  alias Caddy.{Config, ConfigProvider}
+
+  setup do
+    # Store original bin to restore after test
+    original_config = ConfigProvider.get_config()
+
+    on_exit(fn ->
+      # Restore original configuration
+      if original_config.bin do
+        ConfigProvider.set_bin(original_config.bin)
+      end
+
+      # Clean up any test artifacts
+      if File.exists?(Config.pid_file()) do
+        File.rm(Config.pid_file())
+      end
+    end)
+
+    {:ok, original_config: original_config}
+  end
+
+  describe "Server lifecycle" do
+    test "can retrieve server configuration", %{original_config: _config} do
+      config = ConfigProvider.get_config()
+
+      # Configuration should be a Config struct
+      assert %Config{} = config
+      # Should have a binary path (may be nil if not configured)
+      assert is_binary(config.bin) or is_nil(config.bin)
+    end
+
+    test "set_bin validates the binary path", %{original_config: original} do
+      # Try to set an invalid path - should fail validation
+      result = ConfigProvider.set_bin("/nonexistent/caddy")
+      assert {:error, _reason} = result
+
+      # Config should remain unchanged after failed validation
+      config = ConfigProvider.get_config()
+      assert config.bin == original.bin
+    end
+
+    test "can set global configuration", %{original_config: _original} do
+      global_config = "debug\nauto_https off"
+      ConfigProvider.set_global(global_config)
+      config = ConfigProvider.get_config()
+
+      assert config.global == global_config
+    end
+
+    test "can add site configuration", %{original_config: _original} do
+      site_name = "example.com"
+      site_config = "reverse_proxy localhost:3000"
+
+      ConfigProvider.set_site(site_name, site_config)
+      config = ConfigProvider.get_config()
+
+      assert Map.has_key?(config.sites, site_name)
+      assert config.sites[site_name] == site_config
+    end
+  end
+
+  describe "Configuration validation" do
+    test "validates caddy binary exists" do
+      # Test that validation catches non-existent binaries
+      result = Config.validate_bin("/this/does/not/exist")
+      assert {:error, _message} = result
+    end
+
+    test "validates caddy binary when it exists" do
+      caddy_bin = System.find_executable("caddy")
+
+      if caddy_bin do
+        result = Config.validate_bin(caddy_bin)
+        # Should either be :ok or an error about permissions/version
+        case result do
+          :ok -> assert true
+          {:error, _msg} -> assert true
+        end
+      else
+        assert true
+      end
+    end
+
+    test "rejects non-binary input" do
+      result = Config.validate_bin(123)
+      assert {:error, _} = result
+    end
+  end
+
+  describe "PID file management" do
+    test "pid file path is generated correctly" do
+      pid_file = Config.pid_file()
+      assert is_binary(pid_file)
+      assert String.ends_with?(pid_file, "caddy.pid")
+    end
+
+    test "socket file path is generated correctly" do
+      socket_file = Config.socket_file()
+      assert is_binary(socket_file)
+      assert String.ends_with?(socket_file, "caddy.sock")
+    end
+  end
+
+  describe "Path management" do
+    test "ensures all required paths exist" do
+      result = Config.ensure_path_exists()
+      assert result == true
+
+      # Verify paths were created
+      assert File.dir?(Config.priv_path())
+      assert File.dir?(Config.share_path())
+      assert File.dir?(Config.etc_path())
+      assert File.dir?(Config.run_path())
+      assert File.dir?(Config.tmp_path())
+    end
+  end
+end