diff --git a/modules/unsupported/cql2-text/pom.xml b/modules/unsupported/cql2-text/pom.xml
index 30a47a8f0d5..4b70353c8a6 100644
--- a/modules/unsupported/cql2-text/pom.xml
+++ b/modules/unsupported/cql2-text/pom.xml
@@ -32,6 +32,17 @@
       <classifier>tests</classifier>
       <scope>test</scope>
     </dependency>
+    <dependency>
+      <groupId>commons-io</groupId>
+      <artifactId>commons-io</artifactId>
+      <scope>test</scope>
+    </dependency>
+    <dependency>
+      <groupId>org.geotools</groupId>
+      <artifactId>gt-geopkg</artifactId>
+      <version>${project.version}</version>
+      <scope>test</scope>
+    </dependency>
   </dependencies>
 
   <!-- ==================================================== -->
diff --git a/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ATSOnlineTest.java b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ATSOnlineTest.java
new file mode 100644
index 00000000000..65942f0f3fa
--- /dev/null
+++ b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ATSOnlineTest.java
@@ -0,0 +1,57 @@
+package org.geotools.filter.text.cql_2.conformance;
+
+import java.io.File;
+import java.io.IOException;
+import java.net.URL;
+import java.nio.file.Path;
+import java.util.HashMap;
+import java.util.Map;
+import java.util.TimeZone;
+import org.apache.commons.io.FileUtils;
+import org.geotools.api.data.DataStore;
+import org.geotools.api.data.DataStoreFinder;
+import org.geotools.http.HTTPResponse;
+import org.geotools.http.SimpleHttpClient;
+import org.junit.BeforeClass;
+
+/**
+ * Base class for tests issued from the Abstract Test Suite (ATS). See
+ * https://docs.ogc.org/is/21-065r2/21-065r2.html#ats for the context.
+ *
+ * <p>This class will download the official Natural Earth dataset and store it into the default
+ * temporary directory.
+ */
+public abstract class ATSOnlineTest {
+
+    private static String NE_DATA_URL =
+            "https://github.com/opengeospatial/ogcapi-features/raw/refs/heads/master/cql2/standard/data/ne110m4cql2.gpkg";
+
+    protected final File neGpkg = Path.of(System.getProperty("java.io.tmpdir"), "ne.gpkg").toFile();
+
+    @BeforeClass
+    public static void forceGMT() {
+        TimeZone.setDefault(TimeZone.getTimeZone("GMT"));
+    }
+
+    private void downloadNaturalEarthData() throws IOException {
+        if (neGpkg.exists()) {
+            return;
+        }
+        neGpkg.createNewFile();
+        SimpleHttpClient client = new SimpleHttpClient();
+        HTTPResponse r = client.get(new URL(NE_DATA_URL));
+        FileUtils.copyInputStreamToFile(r.getResponseStream(), neGpkg);
+    }
+
+    protected DataStore naturalEarthData() throws IOException {
+        downloadNaturalEarthData();
+        Map params = new HashMap();
+        params.put("dbtype", "geopkg");
+        params.put("database", neGpkg.getAbsolutePath());
+        params.put("read-only", true);
+
+        DataStore datastore = DataStoreFinder.getDataStore(params);
+
+        return datastore;
+    }
+}
diff --git a/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest13OnlineTest.java b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest13OnlineTest.java
new file mode 100644
index 00000000000..6d3413b4697
--- /dev/null
+++ b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest13OnlineTest.java
@@ -0,0 +1,65 @@
+package org.geotools.filter.text.cql_2.conformance;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import org.geootols.filter.text.cql_2.CQL2;
+import org.geotools.api.data.DataStore;
+import org.geotools.api.filter.Filter;
+import org.geotools.filter.text.cql2.CQLException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+/** See table 9 from section A.4.4 Conformance test 13. */
+@RunWith(Parameterized.class)
+public class ConformanceTest13OnlineTest extends ATSOnlineTest {
+
+    private final String criteria;
+    private final int expectedFeatures;
+
+    public ConformanceTest13OnlineTest(String criteria, int expectedFeatures) {
+        this.criteria = criteria;
+        this.expectedFeatures = expectedFeatures;
+    }
+
+    @Parameterized.Parameters(name = "{index} {0}")
+    public static Collection<Object[]> params() {
+        return Arrays.asList(
+                new Object[][] {
+                    {"name LIKE 'B_r%'", 3},
+                    {"name NOT LIKE 'B_r%'", 240},
+                    {"pop_other between 1000000 and 3000000", 75},
+                    {"pop_other not between 1000000 and 3000000", 168},
+                    {"name IN ('Kiev','kobenhavn','Berlin','athens','foo')", 2},
+                    {"name NOT IN ('Kiev','kobenhavn','Berlin','athens','foo')", 241},
+                    {"pop_other in (1038288,1611692,3013258,3013257,3013259)", 3},
+                    {"pop_other not in (1038288,1611692,3013258,3013257,3013259)", 240},
+                    {"\"date\" in (DATE('2021-04-16'),DATE('2022-04-16'),DATE('2022-04-18'))", 2},
+                    {
+                        "\"date\" not in (DATE('2021-04-16'),DATE('2022-04-16'),DATE('2022-04-18'))",
+                        1
+                    },
+                    {"start in (TIMESTAMP('2022-04-16T10:13:19Z'))", 1},
+                    {"start not in (TIMESTAMP('2022-04-16T10:13:19Z'))", 2},
+                    {"boolean in (true)", 2},
+                    {"boolean not in (false)", 2}
+                });
+    }
+
+    public @Test void testConformance() throws IOException, CQLException {
+        DataStore ds = naturalEarthData();
+        int feat = featuresReturned(ds);
+        ds.dispose();
+
+        assertEquals(this.expectedFeatures, feat);
+    }
+
+    private int featuresReturned(DataStore ds) throws CQLException, IOException {
+        Filter filter = CQL2.toFilter(this.criteria);
+
+        return ds.getFeatureSource("ne_110m_populated_places_simple").getFeatures(filter).size();
+    }
+}
diff --git a/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest26OnlineTest.java b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest26OnlineTest.java
new file mode 100644
index 00000000000..5ea5980b681
--- /dev/null
+++ b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest26OnlineTest.java
@@ -0,0 +1,69 @@
+package org.geotools.filter.text.cql_2.conformance;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import org.geootols.filter.text.cql_2.CQL2;
+import org.geotools.api.data.DataStore;
+import org.geotools.api.filter.Filter;
+import org.geotools.filter.text.cql2.CQLException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+/** See table 12 from section A.7.2 Conformance test 26. */
+@RunWith(Parameterized.class)
+public class ConformanceTest26OnlineTest extends ATSOnlineTest {
+
+    private final String dataset;
+    private final String criteria;
+    private final int expectedFeatures;
+
+    public ConformanceTest26OnlineTest(String dataset, String criteria, int expectedFeatures) {
+        this.dataset = dataset;
+        this.criteria = criteria;
+        this.expectedFeatures = expectedFeatures;
+    }
+
+    @Parameterized.Parameters(name = "{index} {0} {1}")
+    public static Collection<Object[]> params() {
+        return Arrays.asList(
+                new Object[][] {
+                    {"ne_110m_admin_0_countries", "S_INTERSECTS(geom,BBOX(0,40,10,50))", 8},
+                    {"ne_110m_admin_0_countries", "S_INTERSECTS(geom,BBOX(150,-90,-150,90))", 10},
+                    {"ne_110m_admin_0_countries", "S_INTERSECTS(geom,POINT(7.02 49.92))", 1},
+                    {
+                        "ne_110m_admin_0_countries",
+                        "S_INTERSECTS(geom,BBOX(0,40,10,50)) and S_INTERSECTS(geom,BBOX(5,50,10,60))",
+                        3
+                    },
+                    {
+                        "ne_110m_admin_0_countries",
+                        "S_INTERSECTS(geom,BBOX(0,40,10,50)) and not S_INTERSECTS(geom,BBOX(5,50,10,60))",
+                        5
+                    },
+                    {
+                        "ne_110m_admin_0_countries",
+                        "S_INTERSECTS(geom,BBOX(0,40,10,50)) or S_INTERSECTS(geom,BBOX(-90,40,-60,50))",
+                        10
+                    },
+                    {"ne_110m_populated_places_simple", "S_INTERSECTS(geom,BBOX(0,40,10,50))", 7},
+                    {"ne_110m_rivers_lake_centerlines", "S_INTERSECTS(geom,BBOX(-180,-90,0,90))", 4}
+                });
+    }
+
+    public @Test void testConformance() throws CQLException, IOException {
+        DataStore ds = naturalEarthData();
+        int feat = featuresReturned(ds);
+        ds.dispose();
+
+        assertEquals(this.expectedFeatures, feat);
+    }
+
+    private int featuresReturned(DataStore ds) throws CQLException, IOException {
+        Filter filter = CQL2.toFilter(this.criteria);
+        return ds.getFeatureSource(this.dataset).getFeatures(filter).size();
+    }
+}
diff --git a/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest8OnlineTest.java b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest8OnlineTest.java
new file mode 100644
index 00000000000..3ecc2197ba6
--- /dev/null
+++ b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest8OnlineTest.java
@@ -0,0 +1,121 @@
+package org.geotools.filter.text.cql_2.conformance;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import org.geootols.filter.text.cql_2.CQL2;
+import org.geotools.api.data.DataStore;
+import org.geotools.api.filter.Filter;
+import org.geotools.filter.text.cql2.CQLException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+/** See table 7 from section A.3.5 Conformance test 8. */
+@RunWith(Parameterized.class)
+public class ConformanceTest8OnlineTest extends ATSOnlineTest {
+
+    private final String dataset;
+    private final String criteria;
+    private final int expectedFeatures;
+
+    public ConformanceTest8OnlineTest(String dataset, String criteria, int expectedFeatures) {
+        this.dataset = dataset;
+        this.criteria = criteria;
+        this.expectedFeatures = expectedFeatures;
+    }
+
+    @Parameterized.Parameters(name = "{index} {0} {1}")
+    public static Collection<Object[]> params() {
+        return Arrays.asList(
+                new Object[][] {
+                    {"ne_110m_admin_0_countries", "NAME='Luxembourg'", 1},
+                    {"ne_110m_admin_0_countries", "NAME>='Luxembourg'", 84},
+                    {"ne_110m_admin_0_countries", "NAME>'Luxembourg'", 83},
+                    {"ne_110m_admin_0_countries", "NAME<='Luxembourg'", 94},
+                    {"ne_110m_admin_0_countries", "NAME<'Luxembourg'", 93},
+                    {"ne_110m_admin_0_countries", "NAME<>'Luxembourg'", 176},
+                    {"ne_110m_admin_0_countries", "POP_EST=37589262", 1},
+                    {"ne_110m_admin_0_countries", "POP_EST>=37589262", 39},
+                    {"ne_110m_admin_0_countries", "POP_EST>37589262", 38},
+                    {"ne_110m_admin_0_countries", "POP_EST<=37589262", 139},
+                    {"ne_110m_admin_0_countries", "POP_EST<37589262", 138},
+                    {"ne_110m_admin_0_countries", "POP_EST<>37589262", 176},
+                    {"ne_110m_populated_places_simple", "name IS NOT NULL", 243},
+                    {"ne_110m_populated_places_simple", "name IS NULL", 0},
+                    {"ne_110m_populated_places_simple", "name='København'", 1},
+                    {"ne_110m_populated_places_simple", "name>='København'", 137},
+                    {"ne_110m_populated_places_simple", "name>'København'", 136},
+                    {"ne_110m_populated_places_simple", "name<='København'", 107},
+                    {"ne_110m_populated_places_simple", "name<'København'", 106},
+                    {"ne_110m_populated_places_simple", "name<>'København'", 242},
+                    {"ne_110m_populated_places_simple", "pop_other IS NOT NULL", 243},
+                    {"ne_110m_populated_places_simple", "pop_other IS NULL", 0},
+                    {"ne_110m_populated_places_simple", "pop_other=1038288", 1},
+                    {"ne_110m_populated_places_simple", "pop_other>=1038288", 123},
+                    {"ne_110m_populated_places_simple", "pop_other>1038288", 122},
+                    {"ne_110m_populated_places_simple", "pop_other<=1038288", 121},
+                    {"ne_110m_populated_places_simple", "pop_other<1038288", 120},
+                    {"ne_110m_populated_places_simple", "pop_other<>1038288", 242},
+                    {"ne_110m_populated_places_simple", "\"date\" IS NOT NULL", 3},
+                    {"ne_110m_populated_places_simple", "\"date\" IS NULL", 240},
+                    {"ne_110m_populated_places_simple", "\"date\"=DATE('2022-04-16')", 1},
+                    {"ne_110m_populated_places_simple", "\"date\">=DATE('2022-04-16')", 2},
+                    {"ne_110m_populated_places_simple", "\"date\">DATE('2022-04-16')", 1},
+                    {"ne_110m_populated_places_simple", "\"date\"<=DATE('2022-04-16')", 2},
+                    {"ne_110m_populated_places_simple", "\"date\"<DATE('2022-04-16')", 1},
+                    {"ne_110m_populated_places_simple", "\"date\"<>DATE('2022-04-16')", 2},
+                    {"ne_110m_populated_places_simple", "start IS NOT NULL", 3},
+                    {"ne_110m_populated_places_simple", "start IS NULL", 240},
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        1
+                    },
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        1
+                    },
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        1
+                    },
+                    {
+                        "ne_110m_populated_places_simple",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {"ne_110m_populated_places_simple", "boolean IS NOT NULL", 3},
+                    {"ne_110m_populated_places_simple", "boolean IS NULL", 240},
+                    {"ne_110m_populated_places_simple", "boolean=true", 2},
+                    {"ne_110m_populated_places_simple", "boolean=false", 1}
+                });
+    }
+
+    public @Test void testConformance() throws CQLException, IOException {
+        DataStore ds = naturalEarthData();
+        int feat = featuresReturned(ds);
+        ds.dispose();
+
+        assertEquals(this.expectedFeatures, feat);
+    }
+
+    private int featuresReturned(DataStore ds) throws CQLException, IOException {
+        Filter filter = CQL2.toFilter(this.criteria);
+        return ds.getFeatureSource(this.dataset).getFeatures(filter).size();
+    }
+}
diff --git a/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest9OnlineTest.java b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest9OnlineTest.java
new file mode 100644
index 00000000000..9a35e46cee3
--- /dev/null
+++ b/modules/unsupported/cql2-text/src/test/java/org/geotools/filter/text/cql_2/conformance/ConformanceTest9OnlineTest.java
@@ -0,0 +1,586 @@
+package org.geotools.filter.text.cql_2.conformance;
+
+import static org.junit.Assert.assertEquals;
+
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collection;
+import org.geootols.filter.text.cql_2.CQL2;
+import org.geotools.api.data.DataStore;
+import org.geotools.api.filter.Filter;
+import org.geotools.filter.text.cql2.CQLException;
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.junit.runners.Parameterized;
+
+/** See table 8 from section A.3.6 Conformance test 9. */
+@RunWith(Parameterized.class)
+public class ConformanceTest9OnlineTest extends ATSOnlineTest {
+
+    private final String p1;
+    private final String p2;
+    private final String p3;
+    private final String p4;
+    private final int expectedFeatures;
+
+    public ConformanceTest9OnlineTest(
+            String p1, String p2, String p3, String p4, int expectedFeatures) {
+        this.p1 = p1;
+        this.p2 = p2;
+        this.p3 = p3;
+        this.p4 = p4;
+        this.expectedFeatures = expectedFeatures;
+    }
+
+    @Parameterized.Parameters(name = "{index} {0} {1} {2} {3}")
+    public static Collection<Object[]> params() {
+        return Arrays.asList(
+                new Object[][] {
+                    {
+                        "pop_other<>1038288",
+                        "name<>'København'",
+                        "pop_other IS NULL",
+                        "name<'København'",
+                        1
+                    },
+                    {
+                        "pop_other<>1038288",
+                        "name>'København'",
+                        "name<='København'",
+                        "boolean=true",
+                        107
+                    },
+                    {
+                        "start IS NULL",
+                        "pop_other IS NOT NULL",
+                        "pop_other IS NOT NULL",
+                        "pop_other>1038288",
+                        124
+                    },
+                    {
+                        "pop_other<1038288",
+                        "pop_other>1038288",
+                        "pop_other IS NULL",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        121
+                    },
+                    {
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other<1038288",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<>'København'",
+                        2
+                    },
+                    {
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<>'København'",
+                        "boolean=true",
+                        "name<'København'",
+                        2
+                    },
+                    {
+                        "pop_other=1038288",
+                        "start IS NULL",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean IS NOT NULL",
+                        242
+                    },
+                    {
+                        "start IS NULL",
+                        "pop_other>1038288",
+                        "start IS NOT NULL",
+                        "name>'København'",
+                        122
+                    },
+                    {
+                        "pop_other<1038288",
+                        "name<>'København'",
+                        "name='København'",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NOT NULL",
+                        "start IS NULL",
+                        "pop_other<1038288",
+                        120
+                    },
+                    {
+                        "name>='København'",
+                        "start IS NOT NULL",
+                        "boolean=true",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        137
+                    },
+                    {
+                        "start IS NOT NULL",
+                        "name>='København'",
+                        "start IS NOT NULL",
+                        "name IS NOT NULL",
+                        3
+                    },
+                    {
+                        "name IS NULL",
+                        "name<'København'",
+                        "pop_other IS NOT NULL",
+                        "boolean IS NOT NULL",
+                        243
+                    },
+                    {
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name>'København'",
+                        "pop_other=1038288",
+                        "name<'København'",
+                        3
+                    },
+                    {
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<='København'",
+                        "boolean IS NULL",
+                        "name>'København'",
+                        138
+                    },
+                    {
+                        "pop_other IS NOT NULL",
+                        "start IS NULL",
+                        "pop_other>=1038288",
+                        "name>'København'",
+                        62
+                    },
+                    {
+                        "name='København'",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean=true",
+                        "pop_other IS NULL",
+                        243
+                    },
+                    {
+                        "name>'København'",
+                        "pop_other<1038288",
+                        "pop_other>1038288",
+                        "name<='København'",
+                        122
+                    },
+                    {
+                        "pop_other<>1038288",
+                        "name='København'",
+                        "name<='København'",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        243
+                    },
+                    {
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other=1038288",
+                        "start IS NULL",
+                        3
+                    },
+                    {
+                        "name<>'København'",
+                        "boolean=true",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start IS NULL",
+                        2
+                    },
+                    {
+                        "name IS NULL",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NULL",
+                        243
+                    },
+                    {
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name>'København'",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NOT NULL",
+                        3
+                    },
+                    {
+                        "name<>'København'",
+                        "pop_other<>1038288",
+                        "pop_other<1038288",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "boolean IS NULL",
+                        "pop_other>1038288",
+                        "boolean IS NOT NULL",
+                        "pop_other IS NULL",
+                        122
+                    },
+                    {
+                        "pop_other=1038288",
+                        "start IS NULL",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other IS NOT NULL",
+                        2
+                    },
+                    {"pop_other<>1038288", "start IS NULL", "pop_other>1038288", "boolean=true", 2},
+                    {
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other<1038288",
+                        "name<='København'",
+                        "pop_other=1038288",
+                        2
+                    },
+                    {
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<='København'",
+                        "name<>'København'",
+                        107
+                    },
+                    {"boolean=true", "name IS NOT NULL", "boolean IS NULL", "pop_other=1038288", 1},
+                    {
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other=1038288",
+                        "pop_other<1038288",
+                        "name<>'København'",
+                        122
+                    },
+                    {
+                        "pop_other<>1038288",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start IS NOT NULL",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        3
+                    },
+                    {
+                        "name<>'København'",
+                        "pop_other<>1038288",
+                        "pop_other IS NOT NULL",
+                        "name IS NOT NULL",
+                        243
+                    },
+                    {
+                        "name='København'",
+                        "pop_other<1038288",
+                        "start IS NOT NULL",
+                        "pop_other<>1038288",
+                        3
+                    },
+                    {
+                        "name<'København'",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "boolean=true",
+                        "pop_other<1038288",
+                        "name IS NOT NULL",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        3
+                    },
+                    {
+                        "pop_other<=1038288",
+                        "name<'København'",
+                        "pop_other<1038288",
+                        "pop_other<1038288",
+                        243
+                    },
+                    {
+                        "pop_other IS NULL",
+                        "name<='København'",
+                        "name='København'",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        2
+                    },
+                    {
+                        "pop_other<1038288",
+                        "name<>'København'",
+                        "pop_other<>1038288",
+                        "name<>'København'",
+                        243
+                    },
+                    {
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other IS NULL",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NOT NULL",
+                        2
+                    },
+                    {
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name='København'",
+                        "boolean IS NULL",
+                        "pop_other<>1038288",
+                        241
+                    },
+                    {
+                        "boolean=true",
+                        "pop_other<=1038288",
+                        "name<>'København'",
+                        "pop_other IS NULL",
+                        2
+                    },
+                    {
+                        "name IS NOT NULL",
+                        "pop_other<=1038288",
+                        "start IS NOT NULL",
+                        "boolean IS NOT NULL",
+                        124
+                    },
+                    {
+                        "pop_other<=1038288",
+                        "pop_other<1038288",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other>1038288",
+                        1
+                    },
+                    {
+                        "start IS NOT NULL",
+                        "boolean IS NOT NULL",
+                        "name>='København'",
+                        "pop_other IS NOT NULL",
+                        137
+                    },
+                    {
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start IS NOT NULL",
+                        "pop_other>1038288",
+                        "pop_other<1038288",
+                        1
+                    },
+                    {
+                        "pop_other<=1038288",
+                        "name<='København'",
+                        "boolean IS NULL",
+                        "start IS NOT NULL",
+                        198
+                    },
+                    {
+                        "name>='København'",
+                        "name>='København'",
+                        "name<='København'",
+                        "name>='København'",
+                        107
+                    },
+                    {
+                        "boolean=true",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean IS NOT NULL",
+                        "name<'København'",
+                        2
+                    },
+                    {
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other IS NULL",
+                        "pop_other<=1038288",
+                        1
+                    },
+                    {
+                        "pop_other<1038288",
+                        "name='København'",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<'København'",
+                        181
+                    },
+                    {
+                        "pop_other<1038288",
+                        "pop_other<=1038288",
+                        "pop_other IS NULL",
+                        "start IS NOT NULL",
+                        121
+                    },
+                    {
+                        "name>='København'",
+                        "pop_other>=1038288",
+                        "boolean=true",
+                        "name IS NOT NULL",
+                        79
+                    },
+                    {
+                        "boolean IS NULL",
+                        "name<>'København'",
+                        "boolean IS NULL",
+                        "pop_other IS NOT NULL",
+                        240
+                    },
+                    {
+                        "pop_other<1038288",
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name>'København'",
+                        "pop_other<=1038288",
+                        199
+                    },
+                    {
+                        "name<='København'",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<'København'",
+                        "boolean IS NULL",
+                        106
+                    },
+                    {
+                        "pop_other IS NOT NULL",
+                        "name<>'København'",
+                        "pop_other<1038288",
+                        "pop_other<=1038288",
+                        121
+                    },
+                    {
+                        "name>='København'",
+                        "start IS NOT NULL",
+                        "name>='København'",
+                        "name IS NOT NULL",
+                        137
+                    },
+                    {
+                        "pop_other<1038288",
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NULL",
+                        "pop_other>=1038288",
+                        1
+                    },
+                    {
+                        "pop_other>=1038288",
+                        "name>'København'",
+                        "boolean IS NOT NULL",
+                        "start IS NOT NULL",
+                        184
+                    },
+                    {
+                        "start IS NOT NULL",
+                        "name<>'København'",
+                        "name<='København'",
+                        "name IS NULL",
+                        241
+                    },
+                    {
+                        "name>='København'",
+                        "pop_other<>1038288",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<>'København'",
+                        2
+                    },
+                    {
+                        "boolean IS NOT NULL",
+                        "pop_other<=1038288",
+                        "pop_other=1038288",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        1
+                    },
+                    {
+                        "name IS NOT NULL",
+                        "start IS NOT NULL",
+                        "start IS NOT NULL",
+                        "name>='København'",
+                        241
+                    },
+                    {
+                        "pop_other=1038288",
+                        "pop_other IS NOT NULL",
+                        "start IS NOT NULL",
+                        "name<>'København'",
+                        2
+                    },
+                    {
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start IS NULL",
+                        "pop_other>1038288",
+                        "pop_other<=1038288",
+                        1
+                    },
+                    {
+                        "name IS NULL",
+                        "start IS NOT NULL",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name IS NOT NULL",
+                        1
+                    },
+                    {
+                        "boolean IS NOT NULL",
+                        "name='København'",
+                        "boolean IS NOT NULL",
+                        "name IS NOT NULL",
+                        3
+                    },
+                    {
+                        "pop_other<>1038288",
+                        "pop_other<>1038288",
+                        "pop_other=1038288",
+                        "pop_other<=1038288",
+                        1
+                    },
+                    {
+                        "pop_other IS NULL",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean IS NOT NULL",
+                        241
+                    },
+                    {
+                        "start<TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean IS NULL",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<'København'",
+                        2
+                    },
+                    {
+                        "pop_other>1038288",
+                        "pop_other<>1038288",
+                        "start<>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "name<>'København'",
+                        2
+                    },
+                    {
+                        "start>=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other=1038288",
+                        "name IS NOT NULL",
+                        2
+                    },
+                    {
+                        "pop_other<=1038288",
+                        "start IS NOT NULL",
+                        "start<=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean IS NOT NULL",
+                        242
+                    },
+                    {
+                        "boolean=true",
+                        "start>TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "pop_other<1038288",
+                        "pop_other<>1038288",
+                        122
+                    },
+                    {
+                        "pop_other>=1038288",
+                        "pop_other>1038288",
+                        "boolean IS NULL",
+                        "pop_other=1038288",
+                        121
+                    },
+                    {
+                        "name<'København'",
+                        "pop_other>1038288",
+                        "start=TIMESTAMP('2022-04-16T10:13:19Z')",
+                        "boolean=true",
+                        44
+                    }
+                });
+    }
+
+    public @Test void testConformance() throws IOException, CQLException {
+        DataStore ds = naturalEarthData();
+        int feat = featuresReturned(ds);
+        ds.dispose();
+
+        assertEquals(this.expectedFeatures, feat);
+    }
+
+    private int featuresReturned(DataStore ds) throws CQLException, IOException {
+        Filter filter =
+                CQL2.toFilter(
+                        String.format(
+                                "(NOT (%s) AND %s) OR (%s and %s) or not (%s OR %s)",
+                                p2, p1, p3, p4, p1, p4));
+
+        return ds.getFeatureSource("ne_110m_populated_places_simple").getFeatures(filter).size();
+    }
+}