add --fail-if-no-tests optional arg (#139)

Add --fail-if-no-tests optional arg.

Author: dsvoronin

README.md

@@ -114,7 +114,12 @@ Composer shipped as jar, to run it you need JVM 1.8+: `java -jar composer-latest
   * Default: `120` seconds (2 minutes). 
   * Applicable to both test APK and APK under test. 
   * Example: `--install-timeout 20`
-
+* `--fail-if-no-tests`
+  * Either `true` or `false` to enable/disable error on empty test suite.
+  * Default: `true`.
+  * `False` may be applicable when you run tests conditionally(via annotation/package filters) and empty suite is a valid outcome.
+  * Example: `--fail-if-no-tests false`
+  
 ##### Example
 
 Simplest :

composer/src/main/kotlin/com/gojuno/composer/Args.kt

@@ -97,7 +97,16 @@ data class Args(
                 description = "APK installation timeout in seconds. If not passed defaults to 120 seconds (2 minutes). Applicable to both test APK and APK under test.",
                 order = 10
         )
-        var installTimeoutSeconds: Int = TimeUnit.MINUTES.toSeconds(2).toInt()
+        var installTimeoutSeconds: Int = TimeUnit.MINUTES.toSeconds(2).toInt(),
+
+        @Parameter(
+                names = arrayOf("--fail-if-no-tests"),
+                required = false,
+                arity = 1,
+                description = "Either `true` or `false` to enable/disable error on empty test suite. True by default.",
+                order = 11
+        )
+        var failIfNoTests: Boolean = true
 )
 
 // No way to share array both for runtime and annotation without reflection.

composer/src/main/kotlin/com/gojuno/composer/Main.kt

@@ -74,7 +74,7 @@ fun main(rawArgs: Array<String>) {
 
     when {
         totalPassed > 0 && totalFailed == 0 -> exit(Exit.Ok)
-        totalPassed == 0 && totalFailed == 0 -> exit(Exit.NoTests)
+        totalPassed == 0 && totalFailed == 0 -> if(args.failIfNoTests) exit(Exit.NoTests) else exit(Exit.Ok)
         else -> exit(Exit.ThereWereFailedTests)
     }
 

composer/src/test/kotlin/com/gojuno/composer/ArgsSpec.kt

@@ -29,7 +29,8 @@ class ArgsSpec : Spek({
                     keepOutputOnExit = false,
                     devices = emptyList(),
                     devicePattern = "",
-                    installTimeoutSeconds = 120
+                    installTimeoutSeconds = 120,
+                    failIfNoTests = true
             ))
         }
     }
@@ -164,4 +165,32 @@ class ArgsSpec : Spek({
             assertThat(args.installTimeoutSeconds).isEqualTo(600)
         }
     }
+
+    context("parse args with passed --fail-if-no-tests") {
+
+        val args by memoized {
+            parseArgs(rawArgsWithOnlyRequiredFields + arrayOf("--fail-if-no-tests", "false"))
+        }
+
+        it("parses --fail-if-no-tests correctly") {
+            assertThat(args.failIfNoTests).isEqualTo(false)
+        }
+    }
+
+    context("parse args with explicitly passed --fail-if-no-tests") {
+
+        listOf(true, false).forEach { failIfNoTests ->
+
+            context("--fail-if-no-tests $failIfNoTests") {
+
+                val args by memoized {
+                    parseArgs(rawArgsWithOnlyRequiredFields + arrayOf("--fail-if-no-tests", "$failIfNoTests"))
+                }
+
+                it("parses --fail-if-no-tests correctly") {
+                    assertThat(args.failIfNoTests).isEqualTo(failIfNoTests)
+                }
+            }
+        }
+    }
 })