fix: add build.gradle as root marker for single-module Gradle projects

lua/neotest-java/core/file_checker.lua

@@ -16,6 +16,10 @@ local FileChecker = function(dependencies)
 			local my_path = Path(file_path)
 			local base_dir = dependencies.root_getter()
 
+			if not base_dir then
+				return false
+			end
+
 			local relative_path = my_path:make_relative(base_dir)
 			if relative_path:contains("main") then
 				return false

lua/neotest-java/core/root_finder.lua

@@ -16,6 +16,8 @@ function RootFinder.find_root(dir, matcher)
 		"pom.xml",
 		"settings.gradle",
 		"settings.gradle.kts",
+		"build.gradle",
+		"build.gradle.kts",
 		".git",
 	}
 

tests/unit/file_checker_spec.lua

@@ -80,4 +80,15 @@ describe("file_checker", function()
 			}).is_test_file(file_path))
 		end
 	end)
+
+	it("should return false when root_getter returns nil", function()
+		local file_checker = FileChecker({
+			patterns = patterns,
+			root_getter = function()
+				return nil
+			end,
+		})
+
+		assert.is_false(file_checker.is_test_file("/any/path/Test.java"))
+	end)
 end)

tests/unit/root_finder_spec.lua

@@ -32,4 +32,23 @@ describe("RootFinder", function()
 		-- then
 		assert.is_nil(actualRoot)
 	end)
+
+	it("should find build.gradle before .git for single-module Gradle projects", function()
+		local patterns_checked = {}
+		local matcher = function(pattern)
+			table.insert(patterns_checked, pattern)
+			return function(_)
+				if pattern == "build.gradle" then
+					return "/path/to/project"
+				end
+				return nil
+			end
+		end
+
+		local root = root_finder.find_root("/some/dir", matcher)
+
+		assert.are.same("/path/to/project", root)
+		assert.is_true(patterns_checked[#patterns_checked] == "build.gradle")
+		assert.is_true(patterns_checked[#patterns_checked - 1] ~= ".git")
+	end)
 end)