diff --git a/README.md b/README.md
index 7a209d1..32e3cab 100644
--- a/README.md
+++ b/README.md
@@ -1,5 +1,6 @@
 # kargo
-A command-line build tool for kotlin inspired by rust's [cargo](https://doc.rust-lang.org/cargo/). 
+
+A command-line build tool for kotlin inspired by rust's [cargo](https://doc.rust-lang.org/cargo/).
 
 # Installation
 
@@ -78,6 +79,7 @@ Builds your project using the kotlin CLI compiler. This will produce a jar file
 in `target/<project.name>.jar` containing your code and the kotlin runtime.
 
 ### run
+
 `kargo run [--script <path to kts script>] [-- <args to main class or script>]`
 
 Run the project's main class with the provided args, or alternately the
@@ -116,6 +118,26 @@ any errors.
 
 Uses [`ktlint`](https://ktlint.github.io/) to format your kotlin sources
 in-place. This command is known not to work on java 17.
+:w
+
+### test
+
+`kargo test`
+Uses JUnit5 to run the project's tests, which should do annotations / assertions via the
+standard `kotlin.test` library. (You must also add a
+`org.jetbrains.kotlin:kotlin-test-junit5` dependency to `Kargo.toml` for test running.)
+
+To avoid confusion / mistakenly thinking that tests passed when they didn't,
+this will run `kargo build` before running tests.
+
+Test discovery requires some knowledge of project layout. By default, kargo will
+discover all test files ending in `_test.kt` within the `src` directory. To use
+the more conventional `src/{main,test}/kotlin` project layout, add
+`project_layout = "classic"` to the package section of the `Kargo.toml` file.
+
+It's a known issue that we currently don't discover functions annotated with
+@Test at top-level in test files. As a workaround, place them within classes
+whose name starts or ends with `Test`.
 
 ## Kargo.toml reference
 
@@ -131,6 +153,10 @@ in-place. This command is known not to work on java 17.
 - `use_serialization_plugin` (optional, default `false`): if you use
   `kotlinx.serialization` in your project, set this to `true` to enable the
   corresponding compiler plugin.
+- `project_layout` (optional, one of `classic` or `flat`, default `flat`): project
+  layout used to discover tests. `flat` allows test files alongside code, in
+  files ending in `_test.kt`. `classic` uses the more conventional layout where
+  tests are in `src/test` (and non-test code is in `src/main`).
 
 `[dependencies]`: this section is required but can be empty
 
@@ -151,15 +177,18 @@ itself.
 
 ### Short-term
 
-- `kargo test` for running tests (and exclusion of test files from builds, etc.)
+- test configuration options for running tests by tag, or specific tests
+- test discovery for top-level functions
 - a number of other configuration options (option to turn off including the
   kotlin runtime in the jar, support of other source / test layouts, etc.)
 
 ### Medium-term
+
 - better support for building / publishing libraries, rather than just runnable
   applications
 
 ### Long-term
+
 - kotlin js/native support
 
 ## License
diff --git a/src/commands/Run.kt b/src/commands/Run.kt
index 7241281..42f9490 100644
--- a/src/commands/Run.kt
+++ b/src/commands/Run.kt
@@ -31,5 +31,4 @@ class Run(val script: Path?, val runArgs: List<String>) : Runnable {
             KotlinC.script(script, runArgs)
         }
     }
-
 }
diff --git a/src/tools/JUnitRunner.kt b/src/tools/JUnitRunner.kt
index be93a1a..d8ba280 100644
--- a/src/tools/JUnitRunner.kt
+++ b/src/tools/JUnitRunner.kt
@@ -2,10 +2,8 @@ package kargo.tools
 
 import kargo.Config
 import kargo.Subprocess
-import kargo.commands.Run
 import kargo.recListPath
 import kargo.toClasspathString
-import java.io.File
 import java.nio.file.Path
 import kotlin.io.path.absolutePathString
 import kotlin.io.path.div
@@ -22,10 +20,12 @@ object JUnitRunner : Tool {
     fun test() {
         KotlinC.buildTests()
         val testClasses = recListPath(KotlinC.testOutputDir()).filter { it.extension == "class" }
-        val classPath = (Config.global.depsJarFiles() + listOf(
-            KotlinC.outputJar(),
-            KotlinC.testOutputDir(),
-        )).toClasspathString()
+        val classPath = (
+            Config.global.depsJarFiles() + listOf(
+                KotlinC.outputJar(),
+                KotlinC.testOutputDir(),
+            )
+            ).toClasspathString()
         Subprocess.jar(executable().absolutePathString()) {
             addArgs("-cp", classPath)
             arg("--fail-if-no-tests")
diff --git a/src/tools/KotlinC.kt b/src/tools/KotlinC.kt
index 3bd0b2b..930f50a 100644
--- a/src/tools/KotlinC.kt
+++ b/src/tools/KotlinC.kt
@@ -36,7 +36,6 @@ object KotlinC : ToolZipBundle<KotlinCBundle> {
         super.download()
     }
 
-
     fun script(script: Path, scriptArgs: List<String>) {
         Subprocess.new {
             command = path(KotlinCBundle.KOTLINC).absolutePathString()