Add basic argument parsing test

src/main/kotlin/slack/cli/exec/ProcessedExecCli.kt

@@ -31,6 +31,7 @@ import kotlin.io.path.deleteRecursively
 import kotlin.system.exitProcess
 import okio.buffer
 import okio.source
+import org.jetbrains.annotations.TestOnly
 import slack.cli.projectDirOption
 
 /**
@@ -44,17 +45,21 @@ import slack.cli.projectDirOption
 public class ProcessedExecCli :
   CliktCommand("Executes a command with Bugsnag tracing and retries as needed.") {
 
-  private val projectDir by projectDirOption()
-  private val verbose by option("--verbose", "-v").flag()
-  private val bugsnagKey by option("--bugsnag-key", envvar = "PE_BUGSNAG_KEY")
-  private val configurationFile by
+  internal val projectDir by projectDirOption()
+  internal val verbose by option("--verbose", "-v").flag()
+  internal val bugsnagKey by option("--bugsnag-key", envvar = "PE_BUGSNAG_KEY")
+  internal val configurationFile by
     option("--config", envvar = "PE_CONFIGURATION_FILE")
       .path(mustExist = true, canBeFile = true, canBeDir = false)
 
-  private val args by argument().multiple()
+  @get:TestOnly internal val parseOnly by option("--parse-only").flag(default = false)
+
+  internal val args by argument().multiple()
 
   @OptIn(ExperimentalStdlibApi::class, ExperimentalPathApi::class)
   override fun run() {
+    if (parseOnly) return
+
     val moshi = ProcessingUtil.newMoshi()
     val config =
       configurationFile?.let {

src/test/kotlin/slack/cli/exec/ProcessedExecCliTest.kt

@@ -0,0 +1,53 @@
+/*
+ * Copyright (C) 2023 Slack Technologies, LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *    https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package slack.cli.exec
+
+import com.google.common.truth.Truth.assertThat
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+
+class ProcessedExecCliTest {
+
+  @JvmField @Rule val temporaryFolder = TemporaryFolder()
+
+  @Test
+  fun standardParsing() {
+    val configFile = temporaryFolder.newFile("config.json")
+    val args = "./gradlew build -Pvariant=debug"
+    val parsed =
+      ProcessedExecCli().apply {
+        parse(
+          arrayOf(
+            "--project-dir",
+            temporaryFolder.root.absolutePath,
+            "--bugsnag-key=1234",
+            "--verbose",
+            "--parse-only",
+            "--config",
+            configFile.absolutePath,
+            "--",
+            args
+          )
+        )
+      }
+    assertThat(parsed.projectDir).isEqualTo(temporaryFolder.root.toPath())
+    assertThat(parsed.verbose).isTrue()
+    assertThat(parsed.bugsnagKey).isEqualTo("1234")
+    assertThat(parsed.configurationFile).isEqualTo(configFile.toPath())
+    assertThat(parsed.args).isEqualTo(listOf(args))
+  }
+}