support varargs formatter, fixes #70

pom.xml

@@ -22,6 +22,8 @@
     <jgiven.version>1.2.2</jgiven.version>
     <spring-boot.version>2.3.7.RELEASE</spring-boot.version>
 
+    <!-- TEST -->
+    <assertj.version>3.23.1</assertj.version>
   </properties>
 
   <dependencyManagement>
@@ -63,6 +65,13 @@
       <scope>test</scope>
     </dependency>
 
+    <dependency>
+      <groupId>org.assertj</groupId>
+      <artifactId>assertj-core</artifactId>
+      <version>${assertj.version}</version>
+      <scope>test</scope>
+    </dependency>
+
     <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-simple</artifactId>

src/main/kotlin/io/toolisticon/testing/jgiven/format/VarargsFormatter.kt

@@ -0,0 +1,53 @@
+package io.toolisticon.testing.jgiven.format
+
+import com.tngtech.jgiven.annotation.Format
+import com.tngtech.jgiven.format.ArgumentFormatter
+import com.tngtech.jgiven.format.PrintfFormatter
+import kotlin.annotation.AnnotationRetention.RUNTIME
+import kotlin.annotation.AnnotationTarget.*
+
+
+/**
+ * Varargs step parameters annotated with this annotation will be put into quotes (" ") in reports.
+ */
+@MustBeDocumented
+@Format(value = VarargsFormatter::class, args = ["\"%s\""])
+@Target(FIELD, VALUE_PARAMETER, ANNOTATION_CLASS)
+@Retention(RUNTIME)
+annotation class VarargsQuoted
+
+/**
+ * Argument formatter for varargs delegating to [PrintfFormatter]
+ */
+class VarargsFormatter @JvmOverloads constructor(private val delimiter: String = ", ") : ArgumentFormatter<Any?> {
+  companion object {
+    fun anyToList(instance: Any?): List<Any?>? {
+      if (instance == null || !instance::class.java.isArray) {
+        return null
+      }
+
+      // deal with the various primitive array (int[],...) wrappers in kotlin.
+      return when (instance) {
+        is IntArray -> instance.toList()
+        is ByteArray -> instance.toList()
+        is CharArray -> instance.toList()
+        is ShortArray -> instance.toList()
+        is LongArray -> instance.toList()
+        is DoubleArray -> instance.toList()
+        is FloatArray -> instance.toList()
+        is BooleanArray -> instance.toList()
+        else -> (instance as Array<*>).toList()
+      }
+    }
+  }
+
+  private val formatter = PrintfFormatter()
+
+  override fun format(argumentToFormat: Any?, vararg formatterArguments: String): String {
+    val argumentList = anyToList(argumentToFormat)
+
+    return argumentList
+      ?.joinToString(separator = delimiter) { formatter.format(it, *formatterArguments) }
+      ?: formatter.format(argumentToFormat, *formatterArguments)
+  }
+}

src/test/kotlin/io/toolisticon/testing/jgiven/CalculatorExampleTest.kt

@@ -4,6 +4,7 @@ import com.tngtech.jgiven.Stage
 import com.tngtech.jgiven.annotation.ScenarioState
 import com.tngtech.jgiven.annotation.ScenarioState.Resolution.NAME
 import com.tngtech.jgiven.junit5.SimpleScenarioTest
+import io.toolisticon.testing.jgiven.format.VarargsQuoted
 import org.junit.jupiter.api.Test
 import kotlin.test.assertEquals
 
@@ -25,6 +26,18 @@ internal class CalculatorExampleTest : SimpleScenarioTest<CalculatorStage>() {
     THEN
       .`the sum is $`(11)
   }
+
+  @Test
+  fun `calculator adds two numbers as varargs`() {
+    GIVEN
+      .`numbers are $`(5, 4)
+
+    WHEN
+      .`both numbers are added`()
+
+    THEN
+      .`the sum is $`(9)
+  }
 }
 
 @JGivenKotlinStage
@@ -39,6 +52,14 @@ class CalculatorStage : Stage<CalculatorStage>() {
   @ScenarioState(resolution = NAME)
   var sum: Int = 0
 
+  /**
+   * Sets both numbers via vararg, use to verify Vararg formatter.
+   */
+  fun `numbers are $`(@VarargsQuoted vararg nums: Int) = step {
+    require(nums.size == 2) { "need to pass two numbers" }
+    `the first number is $`(nums[0]).`the second number is $`(nums[1])
+  }
+
   fun `the first number is $`(n: Int) = step {
     this.firstNumber = n
   }

src/test/kotlin/io/toolisticon/testing/jgiven/format/VarargsFormatterTest.kt

@@ -0,0 +1,77 @@
+package io.toolisticon.testing.jgiven.format
+
+import io.toolisticon.testing.jgiven.format.VarargsFormatter.Companion.anyToList
+import org.assertj.core.api.Assertions.assertThat
+import org.assertj.core.api.Assertions.assertThatThrownBy
+import org.junit.jupiter.api.Nested
+import org.junit.jupiter.api.Test
+
+
+internal class VarargsFormatterTest {
+
+  private var formatter: VarargsFormatter = VarargsFormatter()
+
+
+  @Test
+  fun `format a single value`() {
+    assertThat(formatter.format("value", "\"%s\"")).isEqualTo("\"value\"")
+  }
+
+  @Test
+  fun `format single array values`() {
+    val varargs = arrayOf("value")
+    assertThat(formatter.format(varargs, "\"%s\"")).isEqualTo("\"value\"")
+  }
+
+  @Test
+  fun `format multiple array values`() {
+    val varargs = arrayOf<Any>("value1", 1L)
+    assertThat(formatter.format(varargs, "\"%s\"")).isEqualTo("\"value1\", \"1\"")
+  }
+
+  @Test
+  fun `fail without formatterArguments`() {
+    val varargs = arrayOf("value")
+
+    assertThatThrownBy { formatter.format(varargs) }
+      .isInstanceOf(ArrayIndexOutOfBoundsException::class.java)
+  }
+
+  @Test
+  fun `format null value`() {
+    val varargs: Array<String>? = null
+    assertThat(formatter.format(varargs, "\"%s\"")).isEqualTo("\"null\"")
+  }
+
+  @Nested
+  inner class AnyToList {
+
+
+    @Test
+    fun `null to null`() {
+      assertThat(anyToList(null)).isNull()
+    }
+
+    @Test
+    fun `non-array to null`() {
+      assertThat(anyToList("")).isNull()
+    }
+
+    @Test
+    fun `int to list`() {
+      val list: List<Any?> = requireNotNull(anyToList(varargInt(1, 2, 3)))
+
+      assertThat(list).containsExactly(1, 2, 3)
+    }
+
+    @Test
+    fun `boolean to list`() {
+      val list = requireNotNull(anyToList(varargBoolean(true, false, null)))
+
+      assertThat(list).containsExactly(true, false, null)
+    }
+  }
+
+  private fun varargInt(vararg v: Int): Any? = v as Any?
+  private fun varargBoolean(vararg v: Boolean?): Any? = v as Any?
+}