Merge pull request #12 from kris7t/xtext-serialization

Make sure Xtext serialization works

15 files changed, 242 insertions, 26 deletions

diff --git a/language-model/META-INF/MANIFEST.MF b/language-model/META-INF/MANIFEST.MF
index 88725730..96617f85 100644
--- a/language-model/META-INF/MANIFEST.MF
+++ b/language-model/META-INF/MANIFEST.MF
@@ -12,5 +12,6 @@ Export-Package: tools.refinery.language.model.problem,
  tools.refinery.language.model.problem.impl,
  tools.refinery.language.model.problem.util
 Require-Bundle: org.eclipse.emf.ecore;visibility:=reexport,
+ org.eclipse.emf.ecore.xmi;visibility:=reexport,
  org.eclipse.core.runtime
 Bundle-ActivationPolicy: lazy
diff --git a/language-model/src/main/java/tools/refinery/language/model/GenerateProblemModel.mwe2 b/language-model/src/main/java/tools/refinery/language/model/GenerateProblemModel.mwe2
index 7f998448..c1518b4d 100644
--- a/language-model/src/main/java/tools/refinery/language/model/GenerateProblemModel.mwe2
+++ b/language-model/src/main/java/tools/refinery/language/model/GenerateProblemModel.mwe2
@@ -3,7 +3,7 @@ module tools.refinery.language.model.GenerateProblemModel
 Workflow {
         bean = org.eclipse.emf.mwe.utils.StandaloneSetup {
                 projectMapping = {
-                        projectName = "language-model"
+                        projectName = "refinery-language-model"
                         path = "."
                 }
         }
@@ -14,7 +14,7 @@ Workflow {
 
         component = org.eclipse.emf.mwe2.ecore.EcoreGenerator {
                 generateCustomClasses = false
-                genModel = "platform:/resource/language-model/src/main/resources/model/problem.genmodel"
-                srcPath = "platform:/resource/language-model/src/main/emf-gen"
+                genModel = "platform:/resource/refinery-language-model/src/main/resources/model/problem.genmodel"
+                srcPath = "platform:/resource/refinery-language-model/src/main/emf-gen"
         }
 }
diff --git a/language-model/src/main/resources/model/problem.ecore b/language-model/src/main/resources/model/problem.ecore
index 77211b66..582f67c8 100644
--- a/language-model/src/main/resources/model/problem.ecore
+++ b/language-model/src/main/resources/model/problem.ecore
@@ -3,7 +3,7 @@
     xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" name="problem" nsURI="https://refinery.tools/emf/2021/Problem" nsPrefix="problem">
   <eClassifiers xsi:type="ecore:EClass" name="Problem" eSuperTypes="#//NamedElement">
     <eStructuralFeatures xsi:type="ecore:EReference" name="nodes" upperBound="-1"
-        eType="#//Node" containment="true"/>
+        eType="#//Node" transient="true" containment="true"/>
     <eStructuralFeatures xsi:type="ecore:EReference" name="statements" upperBound="-1"
         eType="#//Statement" containment="true"/>
   </eClassifiers>
@@ -15,7 +15,7 @@
     <eStructuralFeatures xsi:type="ecore:EReference" name="referenceDeclarations"
         upperBound="-1" eType="#//ReferenceDeclaration" containment="true"/>
     <eStructuralFeatures xsi:type="ecore:EReference" name="newNode" eType="#//Node"
-        containment="true"/>
+        transient="true" containment="true"/>
   </eClassifiers>
   <eClassifiers xsi:type="ecore:EClass" name="ReferenceDeclaration" eSuperTypes="#//Relation">
     <eStructuralFeatures xsi:type="ecore:EReference" name="referenceType" eType="#//Relation"/>
@@ -52,7 +52,7 @@
   <eClassifiers xsi:type="ecore:EClass" name="ExistentialQuantifier" abstract="true"
       interface="true">
     <eStructuralFeatures xsi:type="ecore:EReference" name="implicitVariables" upperBound="-1"
-        eType="#//ImplicitVariable" containment="true"/>
+        eType="#//ImplicitVariable" transient="true" containment="true"/>
   </eClassifiers>
   <eClassifiers xsi:type="ecore:EClass" name="Assertion" eSuperTypes="#//Statement">
     <eStructuralFeatures xsi:type="ecore:EReference" name="relation" eType="#//Relation"/>
@@ -95,7 +95,7 @@
   <eClassifiers xsi:type="ecore:EClass" name="VariableOrNodeArgument" eSuperTypes="#//Argument">
     <eStructuralFeatures xsi:type="ecore:EReference" name="variableOrNode" eType="#//VariableOrNode"/>
     <eStructuralFeatures xsi:type="ecore:EReference" name="singletonVariable" eType="#//ImplicitVariable"
-        containment="true"/>
+        transient="true" containment="true"/>
   </eClassifiers>
   <eClassifiers xsi:type="ecore:EClass" name="EnumDeclaration" eSuperTypes="#//Relation #//Statement">
     <eStructuralFeatures xsi:type="ecore:EReference" name="literals" upperBound="-1"
diff --git a/language-model/src/main/resources/model/problem.genmodel b/language-model/src/main/resources/model/problem.genmodel
index 094533e7..3e0ee35e 100644
--- a/language-model/src/main/resources/model/problem.genmodel
+++ b/language-model/src/main/resources/model/problem.genmodel
@@ -1,7 +1,7 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <genmodel:GenModel xmi:version="2.0" xmlns:xmi="http://www.omg.org/XMI" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
     xmlns:ecore="http://www.eclipse.org/emf/2002/Ecore" xmlns:genmodel="http://www.eclipse.org/emf/2002/GenModel"
-    modelDirectory="/language-model/src/main/emf-gen" creationIcons="false"
+    modelDirectory="/refinery-language-model/src/main/emf-gen" creationIcons="false"
     editDirectory="/language-edit/src/main/emf-gen" editorDirectory="/org.eclipse.viatra.solver.language.model.editor/src-gen"
     modelPluginID="language-model" modelName="Problem" rootExtendsClass="org.eclipse.emf.ecore.impl.MinimalEObjectImpl$Container"
     codeFormatting="true" importerID="org.eclipse.emf.importer.ecore" complianceLevel="5.0"
diff --git a/language-to-store/src/test/java/tools/refinery/language/mapping/tests/PartialModelMapperTest.xtend b/language-to-store/src/test/java/tools/refinery/language/mapping/tests/PartialModelMapperTest.xtend
index add73c87..b2fcbaa9 100644
--- a/language-to-store/src/test/java/tools/refinery/language/mapping/tests/PartialModelMapperTest.xtend
+++ b/language-to-store/src/test/java/tools/refinery/language/mapping/tests/PartialModelMapperTest.xtend
@@ -290,7 +290,7 @@ class PartialModelMapperTest {
                         error invalidTaxStatus(Person p) <->
                                 taxStatus(p, child), children(p, _q).
                         
-                        individual family.
+                        indiv family.
                         Family(family).
                         members(family, anne): true.
                         members(family, bob).
diff --git a/language-web/src/main/js/index.tsx b/language-web/src/main/js/index.tsx
index 3e077ba8..d368c9ba 100644
--- a/language-web/src/main/js/index.tsx
+++ b/language-web/src/main/js/index.tsx
@@ -38,7 +38,7 @@ direct rule createChild(p):
     children(p, q) = true,
     taxStatus(q, child) = true.
 
-individual family.
+indiv family.
 Family(family).
 members(family, anne).
 members(family, bob).
diff --git a/language-web/src/main/js/language/problem.grammar b/language-web/src/main/js/language/problem.grammar
index 0cbfa831..bccc2e31 100644
--- a/language-web/src/main/js/language/problem.grammar
+++ b/language-web/src/main/js/language/problem.grammar
@@ -35,7 +35,7 @@ statement {
     IndividualNodeName ":" Constant "."
   } |
   IndividualDeclaration {
-    ckw<"individual"> sep<",", IndividualNodeName> "."
+    ckw<"indiv"> sep<",", IndividualNodeName> "."
   } |
   ScopeDeclaration {
     kw<"scope"> sep<",", ScopeElement> "."
diff --git a/language-web/src/main/js/language/problemLanguageSupport.ts b/language-web/src/main/js/language/problemLanguageSupport.ts
index 1dba3447..6508a2c0 100644
--- a/language-web/src/main/js/language/problemLanguageSupport.ts
+++ b/language-web/src/main/js/language/problemLanguageSupport.ts
@@ -27,7 +27,7 @@ const parserWithMetadata = (parser as LRParser).configure({
     styleTags({
       LineComment: t.lineComment,
       BlockComment: t.blockComment,
-      'problem class enum pred rule individual scope': t.definitionKeyword,
+      'problem class enum pred rule indiv scope': t.definitionKeyword,
       'abstract extends refers contains opposite error direct default': t.modifier,
       'true false unknown error': t.keyword,
       'new delete': t.operatorKeyword,
diff --git a/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java b/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
index d34a1610..a26ce040 100644
--- a/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
+++ b/language-web/src/test/java/tools/refinery/language/web/ProblemWebSocketServletIntegrationTest.java
@@ -96,7 +96,7 @@ class ProblemWebSocketServletIntegrationTest {
                         case 0 -> session.getRemote().sendString(
                                         "{\"id\":\"foo\",\"request\":{\"resource\":\"test.problem\",\"serviceType\":\"update\",\"fullText\":\"class Person.\n\"}}");
                         case 3 -> session.getRemote().sendString(
-                                        "{\"id\":\"bar\",\"request\":{\"resource\":\"test.problem\",\"serviceType\":\"update\",\"requiredStateId\":\"-80000000\",\"deltaText\":\"individual q.\nnode(q).\n\",\"deltaOffset\":\"0\",\"deltaReplaceLength\":\"0\"}}");
+                                        "{\"id\":\"bar\",\"request\":{\"resource\":\"test.problem\",\"serviceType\":\"update\",\"requiredStateId\":\"-80000000\",\"deltaText\":\"indiv q.\nnode(q).\n\",\"deltaOffset\":\"0\",\"deltaReplaceLength\":\"0\"}}");
                         case 5 -> session.close();
                         }
                 }
diff --git a/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java
index 3229597e..5b8fedba 100644
--- a/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java
+++ b/language-web/src/test/java/tools/refinery/language/web/xtext/servlet/TransactionExecutorTest.java
@@ -92,7 +92,7 @@ class TransactionExecutorTest {
                 var stateId = updateFullText();
                 var responseHandler = sendRequestAndWaitForAllResponses(
                                 new XtextWebRequest("bar", Map.of("resource", RESOURCE_NAME, "serviceType", "update", "requiredStateId",
-                                                stateId, "deltaText", "individual q.\nnode(q).\n", "deltaOffset", "0", "deltaReplaceLength", "0")));
+                                                stateId, "deltaText", "indiv q.\nnode(q).\n", "deltaOffset", "0", "deltaReplaceLength", "0")));
 
                 var captor = newCaptor();
                 verify(responseHandler, times(2)).onResponse(captor.capture());
diff --git a/language/src/main/java/tools/refinery/language/Problem.xtext b/language/src/main/java/tools/refinery/language/Problem.xtext
index b7562759..26773047 100644
--- a/language/src/main/java/tools/refinery/language/Problem.xtext
+++ b/language/src/main/java/tools/refinery/language/Problem.xtext
@@ -109,12 +109,12 @@ ConstantArgument:
 
 Assertion:
         default?="default"?
-        (relation=[Relation|QualifiedName]
-        "(" (arguments+=AssertionArgument ("," arguments+=AssertionArgument)*)? ")"
-        ":" value=LogicValue |
-        value=ShortLogicValue?
+        (value=ShortLogicValue?
         relation=[Relation|QualifiedName]
-        "(" (arguments+=AssertionArgument ("," arguments+=AssertionArgument)*)? ")")
+        "(" (arguments+=AssertionArgument ("," arguments+=AssertionArgument)*)? ")"
+        | relation=[Relation|QualifiedName]
+        "(" (arguments+=AssertionArgument ("," arguments+=AssertionArgument)*)? ")"
+        ":" value=LogicValue)
         ".";
 
 AssertionArgument:
@@ -174,7 +174,7 @@ ExactMultiplicity:
         exactValue=INT;
 
 IndividualDeclaration:
-        "individual" nodes+=EnumLiteral ("," nodes+=EnumLiteral)* ".";
+        "indiv" nodes+=EnumLiteral ("," nodes+=EnumLiteral)* ".";
 
 UpperBound returns ecore::EInt:
         INT | "*";
@@ -184,7 +184,7 @@ QualifiedName hidden():
 
 Identifier:
         ID | "true" | "false" | "unknown" | "error" | "class" | "abstract" | "extends" | "enum" | "pred" |
-        "individual" | "problem" | "new" | "delete" | "direct" | "rule";
+        "indiv" | "problem" | "new" | "delete" | "direct" | "rule";
 
 Integer returns ecore::EInt hidden():
         "-"? INT;
diff --git a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
index 3c10d39e..975fdca2 100644
--- a/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
+++ b/language/src/main/java/tools/refinery/language/validation/ProblemValidator.java
@@ -53,7 +53,7 @@ public class ProblemValidator extends AbstractProblemValidator {
                 var variableOrNode = argument.getVariableOrNode();
                 if (variableOrNode instanceof Node node && !ProblemUtil.isIndividualNode(node)) {
                         var name = node.getName();
-                        var message = "Only individual nodes can be referenced in predicates. Mark '%s' as individual with the declaration 'individual %s.'"
+                        var message = "Only individual nodes can be referenced in predicates. Mark '%s' as individual with the declaration 'indiv %s.'"
                                         .formatted(name, name);
                         error(message, argument, ProblemPackage.Literals.VARIABLE_OR_NODE_ARGUMENT__VARIABLE_OR_NODE,
                                         INSIGNIFICANT_INDEX, NON_INDIVIDUAL_NODE_ISSUE);
diff --git a/language/src/test/java/tools/refinery/language/tests/ProblemParsingTest.xtend b/language/src/test/java/tools/refinery/language/tests/ProblemParsingTest.xtend
index 9e357529..53d31a6c 100644
--- a/language/src/test/java/tools/refinery/language/tests/ProblemParsingTest.xtend
+++ b/language/src/test/java/tools/refinery/language/tests/ProblemParsingTest.xtend
@@ -46,7 +46,7 @@ class ProblemParsingTest {
                         error invalidTaxStatus(Person p) <->
                                 taxStatus(p, child), children(p, _q).
                         
-                        individual family.
+                        indiv family.
                         Family(family).
                         members(family, anne): true.
                         members(family, bob).
diff --git a/language/src/test/java/tools/refinery/language/tests/scoping/NodeScopingTest.xtend b/language/src/test/java/tools/refinery/language/tests/scoping/NodeScopingTest.xtend
index 5f669847..3a046341 100644
--- a/language/src/test/java/tools/refinery/language/tests/scoping/NodeScopingTest.xtend
+++ b/language/src/test/java/tools/refinery/language/tests/scoping/NodeScopingTest.xtend
@@ -81,7 +81,7 @@ class NodeScopingTest {
         def void individualNodeInAssertionTest(String qualifiedNamePrefix, boolean namedProblem) {
                 val it = parseHelper.parse('''
                         «IF namedProblem»problem test.«ENDIF»
-                        individual a, b.
+                        indiv a, b.
                         pred predicate(node x, node y) <-> node(x).
                         predicate(«qualifiedNamePrefix»a, «qualifiedNamePrefix»a).
                         ?predicate(«qualifiedNamePrefix»a, «qualifiedNamePrefix»b).
@@ -99,7 +99,7 @@ class NodeScopingTest {
         def void individualNodeInNodeValueAssertionTest(String qualifiedNamePrefix, boolean namedProblem) {
                 val it = parseHelper.parse('''
                         «IF namedProblem»problem test.«ENDIF»
-                        individual a.
+                        indiv a.
                         «qualifiedNamePrefix»a: 16.
                 ''')
                 assertThat(errors, empty)
@@ -112,7 +112,7 @@ class NodeScopingTest {
         def void individualNodeInPredicateTest(String qualifiedNamePrefix, boolean namedProblem) {
                 val it = parseHelper.parse('''
                         «IF namedProblem»problem test.«ENDIF»
-                        individual b.
+                        indiv b.
                         pred predicate(node a) <-> node(«qualifiedNamePrefix»b).
                 ''')
                 assertThat(errors, empty)
diff --git a/language/src/test/java/tools/refinery/language/tests/serializer/ProblemSerializerTest.java b/language/src/test/java/tools/refinery/language/tests/serializer/ProblemSerializerTest.java
new file mode 100644
index 00000000..802457cb
--- /dev/null
+++ b/language/src/test/java/tools/refinery/language/tests/serializer/ProblemSerializerTest.java
@@ -0,0 +1,215 @@
+package tools.refinery.language.tests.serializer;
+
+import static org.hamcrest.MatcherAssert.assertThat;
+import static org.hamcrest.Matchers.equalTo;
+
+import java.io.ByteArrayOutputStream;
+import java.io.IOException;
+import java.util.Map;
+import java.util.stream.Stream;
+
+import org.eclipse.emf.common.util.URI;
+import org.eclipse.emf.ecore.resource.Resource;
+import org.eclipse.emf.ecore.resource.ResourceSet;
+import org.eclipse.xtext.testing.InjectWith;
+import org.eclipse.xtext.testing.extensions.InjectionExtension;
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.junit.jupiter.params.ParameterizedTest;
+import org.junit.jupiter.params.provider.Arguments;
+import org.junit.jupiter.params.provider.MethodSource;
+
+import com.google.inject.Inject;
+
+import tools.refinery.language.model.ProblemUtil;
+import tools.refinery.language.model.problem.Atom;
+import tools.refinery.language.model.problem.LogicValue;
+import tools.refinery.language.model.problem.Node;
+import tools.refinery.language.model.problem.PredicateDefinition;
+import tools.refinery.language.model.problem.Problem;
+import tools.refinery.language.model.problem.ProblemFactory;
+import tools.refinery.language.model.problem.Relation;
+import tools.refinery.language.model.problem.VariableOrNode;
+import tools.refinery.language.model.tests.ProblemTestUtil;
+import tools.refinery.language.tests.ProblemInjectorProvider;
+
+@ExtendWith(InjectionExtension.class)
+@InjectWith(ProblemInjectorProvider.class)
+public class ProblemSerializerTest {
+        @Inject
+        ResourceSet resourceSet;
+
+        @Inject
+        ProblemTestUtil testUtil;
+
+        Resource resource;
+
+        Problem problem;
+
+        Problem builtin;
+
+        @BeforeEach
+        void beforeEach() {
+                problem = ProblemFactory.eINSTANCE.createProblem();
+                resource = resourceSet.createResource(URI.createFileURI("test.problem"));
+                resource.getContents().add(problem);
+                builtin = ProblemUtil.getBuiltInLibrary(problem).get();
+        }
+
+        @ParameterizedTest
+        @MethodSource
+        void assertionTest(LogicValue value, String serializedAssertion) {
+                var pred = createPred();
+                var node = ProblemFactory.eINSTANCE.createNode();
+                node.setName("a");
+                var individualDeclaration = ProblemFactory.eINSTANCE.createIndividualDeclaration();
+                individualDeclaration.getNodes().add(node);
+                problem.getStatements().add(individualDeclaration);
+                createAssertion(pred, node, value);
+
+                assertSerializedResult("pred foo ( node p ) . indiv a . " + serializedAssertion);
+        }
+
+        static Stream<Arguments> assertionTest() {
+                return Stream.of(Arguments.of(LogicValue.TRUE, "foo ( a ) ."),
+                                Arguments.of(LogicValue.FALSE, "! foo ( a ) ."),
+                                Arguments.of(LogicValue.UNKNOWN, "? foo ( a ) ."),
+                                Arguments.of(LogicValue.ERROR, "foo ( a ) : error ."));
+        }
+
+        @Test
+        void implicitNodeTest() {
+                var pred = createPred();
+                var node = ProblemFactory.eINSTANCE.createNode();
+                node.setName("a");
+                problem.getNodes().add(node);
+                createAssertion(pred, node);
+
+                assertSerializedResult("pred foo ( node p ) . foo ( a ) .");
+        }
+
+        private PredicateDefinition createPred() {
+                var pred = ProblemFactory.eINSTANCE.createPredicateDefinition();
+                pred.setName("foo");
+                var parameter = ProblemFactory.eINSTANCE.createParameter();
+                var nodeType = testUtil.findClass(builtin, "node");
+                parameter.setParameterType(nodeType);
+                parameter.setName("p");
+                pred.getParameters().add(parameter);
+                problem.getStatements().add(pred);
+                return pred;
+        }
+
+        @Test
+        void newNodeTest() {
+                var classDeclaration = ProblemFactory.eINSTANCE.createClassDeclaration();
+                classDeclaration.setName("Foo");
+                var newNode = ProblemFactory.eINSTANCE.createNode();
+                newNode.setName("new");
+                classDeclaration.setNewNode(newNode);
+                problem.getStatements().add(classDeclaration);
+                createAssertion(classDeclaration, newNode);
+
+                assertSerializedResult("class Foo . Foo ( Foo::new ) .");
+        }
+
+        private void createAssertion(Relation relation, Node node) {
+                createAssertion(relation, node, LogicValue.TRUE);
+        }
+
+        private void createAssertion(Relation relation, Node node, LogicValue value) {
+                var assertion = ProblemFactory.eINSTANCE.createAssertion();
+                assertion.setRelation(relation);
+                var argument = ProblemFactory.eINSTANCE.createNodeAssertionArgument();
+                argument.setNode(node);
+                assertion.getArguments().add(argument);
+                assertion.setValue(value);
+                problem.getStatements().add(assertion);
+        }
+
+        @Test
+        void implicitVariableTest() {
+                var pred = ProblemFactory.eINSTANCE.createPredicateDefinition();
+                pred.setName("foo");
+                var nodeType = testUtil.findClass(builtin, "node");
+                var parameter1 = ProblemFactory.eINSTANCE.createParameter();
+                parameter1.setParameterType(nodeType);
+                parameter1.setName("p1");
+                pred.getParameters().add(parameter1);
+                var parameter2 = ProblemFactory.eINSTANCE.createParameter();
+                parameter2.setParameterType(nodeType);
+                parameter2.setName("p2");
+                pred.getParameters().add(parameter2);
+                var conjunction = ProblemFactory.eINSTANCE.createConjunction();
+                var variable = ProblemFactory.eINSTANCE.createImplicitVariable();
+                variable.setName("q");
+                conjunction.getImplicitVariables().add(variable);
+                var equals = testUtil.reference(nodeType, "equals");
+                conjunction.getLiterals().add(createAtom(equals, parameter1, variable));
+                conjunction.getLiterals().add(createAtom(equals, variable, parameter2));
+                pred.getBodies().add(conjunction);
+                problem.getStatements().add(pred);
+
+                assertSerializedResult("pred foo ( node p1 , node p2 ) <-> equals ( p1 , q ) , equals ( q , p2 ) .");
+        }
+
+        private Atom createAtom(Relation relation, VariableOrNode variable1, VariableOrNode variable2) {
+                var atom = ProblemFactory.eINSTANCE.createAtom();
+                atom.setRelation(relation);
+                var arg1 = ProblemFactory.eINSTANCE.createVariableOrNodeArgument();
+                arg1.setVariableOrNode(variable1);
+                atom.getArguments().add(arg1);
+                var arg2 = ProblemFactory.eINSTANCE.createVariableOrNodeArgument();
+                arg2.setVariableOrNode(variable2);
+                atom.getArguments().add(arg2);
+                return atom;
+        }
+
+        @Test
+        void singletonVariableTest() {
+                var pred = ProblemFactory.eINSTANCE.createPredicateDefinition();
+                pred.setName("foo");
+                var nodeType = testUtil.findClass(builtin, "node");
+                var parameter = ProblemFactory.eINSTANCE.createParameter();
+                parameter.setParameterType(nodeType);
+                parameter.setName("p");
+                pred.getParameters().add(parameter);
+                var conjunction = ProblemFactory.eINSTANCE.createConjunction();
+                var atom = ProblemFactory.eINSTANCE.createAtom();
+                var equals = testUtil.reference(nodeType, "equals");
+                atom.setRelation(equals);
+                var arg1 = ProblemFactory.eINSTANCE.createVariableOrNodeArgument();
+                arg1.setVariableOrNode(parameter);
+                atom.getArguments().add(arg1);
+                var arg2 = ProblemFactory.eINSTANCE.createVariableOrNodeArgument();
+                var variable = ProblemFactory.eINSTANCE.createImplicitVariable();
+                variable.setName("_q");
+                arg2.setSingletonVariable(variable);
+                arg2.setVariableOrNode(variable);
+                atom.getArguments().add(arg2);
+                conjunction.getLiterals().add(atom);
+                pred.getBodies().add(conjunction);
+                problem.getStatements().add(pred);
+
+                assertSerializedResult("pred foo ( node p ) <-> equals ( p , _q ) .");
+        }
+
+        private void assertSerializedResult(String expected) {
+                var outputStream = new ByteArrayOutputStream();
+                try {
+                        resource.save(outputStream, Map.of());
+                } catch (IOException e) {
+                        throw new AssertionError("Failed to serialize problem", e);
+                } finally {
+                        try {
+                                outputStream.close();
+                        } catch (IOException e) {
+                                // Nothing to handle in a test.
+                        }
+                }
+                var problemString = outputStream.toString();
+
+                assertThat(problemString, equalTo(expected));
+        }
+}