Enable int, bool, String method parameter conversion

Introduce JsonConverter that converts a single parameter by name from
Json to the parameter type (String, int, or boolean).
Only single parameters are supported right now.

#3

CHANGELOG.md

@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## Unreleased
+### Added
+- Use @JsonConverter to provide actual arguments to tests
+
 ## [1.3.2] - 2018-11-29
 ### Changed
 - Updated to JUnit 5.3.2

build.gradle

@@ -1,11 +1,14 @@
 plugins {
   id "org.sonarqube" version "2.6"
+  id 'idea'
+  id "org.jetbrains.gradle.plugin.idea-ext" version "0.4.2"
 }
 
 apply plugin: 'java-library'
 apply plugin: 'jacoco'
 apply plugin: 'maven-publish'
 apply plugin: 'signing'
+apply plugin: 'idea'
 
 group = 'net.joshka'
 version = '1.3.2'
@@ -19,6 +22,7 @@ targetCompatibility = 1.8
 
 tasks.withType(JavaCompile) {
 	options.encoding = 'UTF-8'
+    options.compilerArgs << '-parameters'
 }
 
 repositories {
@@ -116,3 +120,12 @@ signing {
     useGpgCmd()
     sign publishing.publications.mavenJava
 }
+
+idea.project.settings {
+    compiler {
+        javac {
+            // Necessary for JsonConverter as method parameters otherwise have names like 'arg0', ...
+            javacAdditionalOptions "-parameters"
+        }
+    }
+}

src/main/java/net/joshka/junit/json/params/JsonConverter.java

@@ -0,0 +1,40 @@
+package net.joshka.junit.json.params;
+
+import org.junit.jupiter.api.extension.ParameterContext;
+import org.junit.jupiter.params.converter.ArgumentConversionException;
+import org.junit.jupiter.params.converter.ArgumentConverter;
+
+import javax.json.JsonObject;
+
+public class JsonConverter implements ArgumentConverter {
+
+    /**
+     * Convert the supplied {@code source} object according to the supplied
+     * {@code context}.
+     *
+     * @param source  the source object to convert; may be {@code null}
+     * @param context the parameter context where the converted object will be
+     *                used; never {@code null}
+     * @return the converted object; may be {@code null} but only if the target
+     * type is a reference type
+     * @throws ArgumentConversionException if an error occurs during the
+     *                                     conversion
+     */
+    @Override
+    public Object convert(Object source, ParameterContext context) {
+        if (!(source instanceof JsonObject)) {
+            throw new ArgumentConversionException("Not a JsonObject");
+        }
+        JsonObject json = (JsonObject) source;
+        String name = context.getParameter().getName();
+        Class<?> type = context.getParameter().getType();
+        if (type == String.class) {
+            return json.getString(name);
+        } else if (type == int.class) {
+            return json.getInt(name);
+        } else if (type == boolean.class) {
+            return json.getBoolean(name);
+        }
+        throw new ArgumentConversionException("Can't convert to type: '" + type.getName() + "'");
+    }
+}

src/test/java/net/joshka/junit/json/params/JsonArgumentsToValuesTest.java

@@ -0,0 +1,46 @@
+package net.joshka.junit.json.params;
+
+import org.junit.jupiter.api.Disabled;
+import org.junit.jupiter.api.DisplayName;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.converter.ConvertWith;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+class JsonArgumentsToValuesTest {
+    @ParameterizedTest
+    @JsonSource("{'key':'value'}")
+    @DisplayName("Converts to Strings")
+    void strings(@ConvertWith(JsonConverter.class) String key) {
+        assertEquals("value", key);
+    }
+
+    @ParameterizedTest
+    @JsonSource("{'key': true}")
+    @DisplayName("Converts to booleans")
+    void ints(@ConvertWith(JsonConverter.class) boolean key) {
+        assertTrue(key);
+    }
+
+
+    @ParameterizedTest
+    @JsonSource("{'key': 1 }")
+    @DisplayName("Converts to ints")
+    void booleans(@ConvertWith(JsonConverter.class) int key) {
+        assertEquals(1, key);
+    }
+
+    @ParameterizedTest
+    @Disabled("Doesn't yet work as only the first parameter gets a value")
+    @JsonSource("{'stringKey':'value', 'boolKey': true, 'intKey': 1 }")
+    @DisplayName("provides multiple objects")
+    void multipleObjects(
+            @ConvertWith(JsonConverter.class) String stringKey,
+            @ConvertWith(JsonConverter.class) int intKey,
+            @ConvertWith(JsonConverter.class) boolean boolKey) {
+        assertEquals("value", stringKey);
+        assertTrue(boolKey);
+        assertEquals(1, intKey);
+    }
+}