diff --git a/src/test/java/org/jabref/logic/formatter/bibtexfields/RemoveBracesFormatterTest.java b/src/test/java/org/jabref/logic/formatter/bibtexfields/RemoveBracesFormatterTest.java
index b2f417cd587..45a418094bc 100644
--- a/src/test/java/org/jabref/logic/formatter/bibtexfields/RemoveBracesFormatterTest.java
+++ b/src/test/java/org/jabref/logic/formatter/bibtexfields/RemoveBracesFormatterTest.java
@@ -37,6 +37,11 @@ public void formatKeepsShortString() {
         assertEquals("t", formatter.format("t"));
     }
 
+    @Test
+    public void formatRemovesBracesOnly() {
+        assertEquals("", formatter.format("{}"));
+    }
+
     @Test
     public void formatKeepsEmptyString() {
         assertEquals("", formatter.format(""));
diff --git a/src/test/java/org/jabref/logic/integrity/BracesCorrectorTest.java b/src/test/java/org/jabref/logic/integrity/BracesCorrectorTest.java
index b14d6e5c49f..245829abea3 100644
--- a/src/test/java/org/jabref/logic/integrity/BracesCorrectorTest.java
+++ b/src/test/java/org/jabref/logic/integrity/BracesCorrectorTest.java
@@ -22,6 +22,11 @@ public void inputWithoutBraces() {
         assertEquals("banana", BracesCorrector.apply("banana"));
     }
 
+    @Test
+    public void inputAlreadyCorrect() {
+        assertEquals("{banana}", BracesCorrector.apply("{banana}"));
+    }
+
     @Test
     public void inputMissingClosing() {
         assertEquals("{banana}", BracesCorrector.apply("{banana"));
diff --git a/src/test/java/org/jabref/logic/integrity/CitationKeyDeviationCheckerTest.java b/src/test/java/org/jabref/logic/integrity/CitationKeyDeviationCheckerTest.java
new file mode 100644
index 00000000000..731dbfac2ee
--- /dev/null
+++ b/src/test/java/org/jabref/logic/integrity/CitationKeyDeviationCheckerTest.java
@@ -0,0 +1,51 @@
+package org.jabref.logic.integrity;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.jabref.logic.citationkeypattern.AbstractCitationKeyPattern;
+import org.jabref.logic.citationkeypattern.CitationKeyPatternPreferences;
+import org.jabref.logic.citationkeypattern.GlobalCitationKeyPattern;
+import org.jabref.logic.l10n.Localization;
+import org.jabref.model.database.BibDatabase;
+import org.jabref.model.database.BibDatabaseContext;
+import org.jabref.model.entry.BibEntry;
+import org.jabref.model.entry.field.InternalField;
+import org.jabref.model.entry.field.StandardField;
+import org.jabref.model.metadata.MetaData;
+
+import org.junit.jupiter.api.BeforeEach;
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.when;
+
+public class CitationKeyDeviationCheckerTest {
+
+    private final BibDatabaseContext bibDatabaseContext = mock(BibDatabaseContext.class);
+    private final BibDatabase bibDatabase = mock(BibDatabase.class);
+    private final MetaData metaData = mock(MetaData.class);
+    private final AbstractCitationKeyPattern abstractCitationKeyPattern = mock(AbstractCitationKeyPattern.class);
+    private final GlobalCitationKeyPattern globalCitationKeyPattern = mock(GlobalCitationKeyPattern.class);
+    private final CitationKeyPatternPreferences citationKeyPatternPreferences = mock(CitationKeyPatternPreferences.class);
+    private final CitationKeyDeviationChecker checker = new CitationKeyDeviationChecker(bibDatabaseContext, citationKeyPatternPreferences);
+
+    @BeforeEach
+    void setUp() {
+        when(bibDatabaseContext.getMetaData()).thenReturn(metaData);
+        when(citationKeyPatternPreferences.getKeyPattern()).thenReturn(globalCitationKeyPattern);
+        when(metaData.getCiteKeyPattern(citationKeyPatternPreferences.getKeyPattern())).thenReturn(abstractCitationKeyPattern);
+        when(bibDatabaseContext.getDatabase()).thenReturn(bibDatabase);
+    }
+
+    @Test
+    void citationKeyDeviatesFromGeneratedKey() {
+        BibEntry entry = new BibEntry().withField(InternalField.KEY_FIELD, "Knuth2014")
+                                       .withField(StandardField.AUTHOR, "Knuth")
+                                       .withField(StandardField.YEAR, "2014");
+        List<IntegrityMessage> expected = Collections.singletonList(new IntegrityMessage(
+                Localization.lang("Citation key deviates from generated key"), entry, InternalField.KEY_FIELD));
+        assertEquals(expected, checker.check(entry));
+    }
+}
diff --git a/src/test/java/org/jabref/logic/integrity/CitationKeyDuplicationCheckerTest.java b/src/test/java/org/jabref/logic/integrity/CitationKeyDuplicationCheckerTest.java
new file mode 100644
index 00000000000..b506e87194b
--- /dev/null
+++ b/src/test/java/org/jabref/logic/integrity/CitationKeyDuplicationCheckerTest.java
@@ -0,0 +1,45 @@
+package org.jabref.logic.integrity;
+
+import java.util.Collections;
+import java.util.List;
+
+import org.jabref.logic.l10n.Localization;
+import org.jabref.model.database.BibDatabase;
+import org.jabref.model.entry.BibEntry;
+import org.jabref.model.entry.field.InternalField;
+import org.jabref.model.entry.field.StandardField;
+
+import org.junit.jupiter.api.Test;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+
+public class CitationKeyDuplicationCheckerTest {
+
+    @Test
+    void emptyCitationKey() {
+        BibEntry entry = new BibEntry().withField(InternalField.KEY_FIELD, "")
+                                       .withField(StandardField.AUTHOR, "Knuth")
+                                       .withField(StandardField.YEAR, "2014");
+        BibDatabase bibDatabase = new BibDatabase(List.of(entry));
+        CitationKeyDuplicationChecker checker = new CitationKeyDuplicationChecker(bibDatabase);
+
+        List<IntegrityMessage> expected = Collections.emptyList();
+        assertEquals(expected, checker.check(entry));
+    }
+
+    @Test
+    void hasDuplicateCitationKey() {
+        BibEntry entry = new BibEntry().withField(InternalField.KEY_FIELD, "Knuth2014")
+                                       .withField(StandardField.AUTHOR, "Knuth")
+                                       .withField(StandardField.YEAR, "2014");
+        BibEntry entry2 = new BibEntry().withField(InternalField.KEY_FIELD, "Knuth2014")
+                                        .withField(StandardField.AUTHOR, "Knuth")
+                                        .withField(StandardField.YEAR, "2014");
+        BibDatabase bibDatabase = new BibDatabase(List.of(entry, entry2));
+        CitationKeyDuplicationChecker checker = new CitationKeyDuplicationChecker(bibDatabase);
+
+        List<IntegrityMessage> expected = Collections.singletonList(
+                new IntegrityMessage(Localization.lang("Duplicate citation key"), entry, StandardField.KEY));
+        assertEquals(expected, checker.check(entry));
+    }
+}