Actionable error message when test attempts to access a non-existent data table.

This is usually a minor mistake when the test author provides the type of the DataTable, when actually they need to provide the type of the row.

Author: sambsnyd

rewrite-test/src/main/java/org/openrewrite/test/RecipeSpec.java

@@ -34,6 +34,7 @@
 import java.nio.file.Path;
 import java.util.*;
 import java.util.function.Function;
+import java.util.stream.Collectors;
 
 import static org.assertj.core.api.Assertions.assertThat;
 import static org.assertj.core.api.Assertions.fail;
@@ -209,7 +210,14 @@ public <E> RecipeSpec dataTable(Class<E> rowType, UncheckedConsumer<List<E>> ext
                     return;
                 }
             }
-            fail("No data table found with row type " + rowType);
+            String message = "No data table found with row type: " + rowType;
+            Set<DataTable<?>> tables = run.getDataTables().keySet();
+            if (!tables.isEmpty()) {
+                message += "\nFound data tables row type(s): " + tables.stream()
+                        .map(it -> it.getType().getName().replace("$", "."))
+                        .collect(Collectors.joining(","));
+            }
+            fail(message);
         });
     }