Add array root asserts

README.md

@@ -2,5 +2,47 @@
 
 This library provides helper methods for asserting JSON strings with AssertJ.
 
+Syntax Examples:
+```java
+
+// Assert that a root property is equal to a string
+JsonAssert.assertThat("myprop").isEqualTo("foo");
+
+// Assert that the traversed path exists and the property is larger than two
+JsonAssert.assertThat(JSON).path("a", "b", "c").isEqualTo(2);
+// OR
+JsonAssert.assertThat(JSON).field("a").field("b").field("c").isEqualTo(2);
+
+// Cast property before asserting
+JsonAssert.assertThat(JSON).field("bigdecimal").asBigDecimal().isEqualTo(BigDecimal.valueOf(1234.0));
+
+// Match by regular expression (myprop:"foobar")
+JsonAssert.assertThat(JSON).field("myprop").matches("foo.*")
+    
+// Assert first property in Object matches
+JsonAssert.assertThat(JSON).firstField("lastProp").isEqualTo(1);
+
+// Assert last property in Object matches
+JsonAssert.assertThat(JSON).lastField("lastProp").isEqualTo(3);
+
+// Assert nth property in Object matches
+JsonAssert.assertThat(JSON).nthField("secondProp").isEqualTo(2);
+
+// Assert root typed array "[1,2,3]"
+JsonAssert.assertThat(JSON).asArray(Integer.class).first().isEqualTo(1);
+
+// Assert root array with objects "[{ prop: 1}]"
+JsonAssert.assertThat(JSON).asArray().first().field("prop").isEqualTo(1);
+
+// Assert matrix [[1,2],[3,4]]
+assertThat(JSON).asArray().last().asArray().first().asInteger().isEqualTo(3);
+
+
+
+             
+```
+
+For more examples see the unit tests in [unit tests](src/test/java/com/devsoap/json).
+
 
 Licensed under [CC BY-ND 4.0](https://creativecommons.org/licenses/by-nd/4.0/).

src/main/java/com/devsoap/json/JsonAssert.java

@@ -45,6 +45,35 @@ public class JsonAssert extends AbstractAssert<JsonAssert, String> {
         return assertThat(object.toString());
     }
 
+    public JsonArrayAssert<?> asArray() {
+        try (var stream = new ByteArrayInputStream(actual.getBytes(StandardCharsets.UTF_8))) {
+            var actualParser = Json.createParser(stream);
+            actualParser.next(); // START_ARRAY
+            return typedJsonArray(null, actualParser.getArray());
+        } catch (IOException e) {
+            throw failure("Failed to parse root array");
+        }
+    }
+
+    public <ITEM> ListAssert<ITEM> asArray(Class<ITEM> itemClass) {
+        try (var stream = new ByteArrayInputStream(actual.getBytes(StandardCharsets.UTF_8))) {
+            var actualParser = Json.createParser(stream);
+            actualParser.next(); // START_ARRAY
+            var array =actualParser.getArray();
+            return new ListAssert<>(array.getValuesAs(value -> (ITEM) switch (value.getValueType()) {
+                case ARRAY -> throw failure("Cannot convert ARRAY to %s", itemClass);
+                case OBJECT -> throw failure("Cannot convert OBJECT to %s", itemClass);
+                case STRING -> ((JsonString) value).toString();
+                case NUMBER -> ((JsonNumber) value).intValue();
+                case TRUE -> Boolean.TRUE;
+                case FALSE -> Boolean.FALSE;
+                case NULL -> null;
+            }));
+        } catch (IOException e) {
+            throw failure("Failed to parse root array");
+        }
+    }
+
     public JsonValueAssert<?> firstField(String fieldName) {
         try (var stream = new ByteArrayInputStream(actual.getBytes(StandardCharsets.UTF_8))) {
             var actualParser = Json.createParser(stream);

src/test/java/com/devsoap/json/ArrayTraversalAssertionTest.java

@@ -25,7 +25,7 @@ import static com.devsoap.json.JsonAssert.assertThat;
 public class ArrayTraversalAssertionTest {
 
     private static final String JSON = """
-    {
+    [{
         "array": [
           { "item": 1 },
           { "item": 2 }
@@ -49,18 +49,22 @@ public class ArrayTraversalAssertionTest {
           [1,2],
           [3,4]
         ]
-    }
+    }]
     """;
 
     @Test
-    public void rootArray() {
+    public void rootFieldArray() {
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("array")
                 .first()
                 .field("item")
                 .isEqualTo(1);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("array")
                 .last()
                 .field("item")
@@ -70,6 +74,8 @@ public class ArrayTraversalAssertionTest {
     @Test
     public void fieldArray() {
         assertThat(JSON)
+                .asArray()
+                .first()
                 .field("fieldArray")
                 .array("array")
                 .first()
@@ -77,6 +83,8 @@ public class ArrayTraversalAssertionTest {
                 .isEqualTo(3);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .field("fieldArray")
                 .array("array")
                 .last()
@@ -87,20 +95,31 @@ public class ArrayTraversalAssertionTest {
     @Test
     public void numericArray() {
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("numericArray", Integer.class)
                 .first()
                 .isEqualTo(1);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .field("fieldArray")
                 .array("numericArray", Integer.class)
                 .first()
                 .isEqualTo(1);
+
+        assertThat("[1,2,3]")
+                .asArray(Integer.class)
+                .last()
+                .isEqualTo(3);
     }
 
     @Test
     public void matrix() {
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("matrix")
                 .first()
                 .asArray()
@@ -109,6 +128,8 @@ public class ArrayTraversalAssertionTest {
                 .isEqualTo(1);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("matrix")
                 .first()
                 .asArray()
@@ -117,6 +138,8 @@ public class ArrayTraversalAssertionTest {
                 .isEqualTo(2);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("matrix")
                 .last()
                 .asArray()
@@ -125,6 +148,8 @@ public class ArrayTraversalAssertionTest {
                 .isEqualTo(3);
 
         assertThat(JSON)
+                .asArray()
+                .first()
                 .array("matrix")
                 .last()
                 .asArray()