diff --git a/src/test/kotlin/kestrel/store/sql/DiskExecutorMergeTest.kt b/src/test/kotlin/kestrel/store/sql/DiskExecutorMergeTest.kt
index b98e68b..b8ef6f5 100644
--- a/src/test/kotlin/kestrel/store/sql/DiskExecutorMergeTest.kt
+++ b/src/test/kotlin/kestrel/store/sql/DiskExecutorMergeTest.kt
@@ -313,3 +313,225 @@ class DiskExecutorMergeTest {
         assertEquals(emptyList(), db.select("SELECT * FROM t").rows)
     }
 
+    @Test
+    fun aForeignKeyViolationOnAMergeUpdateIsRejected() {
+        val db = newDatabase()
+        db.run("CREATE TABLE departments (id INTEGER PRIMARY KEY)")
+        db.run("CREATE TABLE employees (id INTEGER PRIMARY KEY, dept_id INTEGER REFERENCES departments(id))")
+        db.run("CREATE TABLE moves (id INTEGER, new_dept INTEGER)")
+        db.run("INSERT INTO departments VALUES (1)")
+        db.run("INSERT INTO employees VALUES (1, 1)")
+        db.run("INSERT INTO moves VALUES (1, 999)")
+        val error = assertFailsWith<KestrelException> {
+            db.run("MERGE INTO employees USING moves ON employees.id = moves.id WHEN MATCHED THEN UPDATE SET dept_id = moves.new_dept")
+        }
+        assertTrue(error.message!!.contains("FOREIGN KEY"), error.message)
+        assertEquals(listOf(listOf(int(1))), db.select("SELECT dept_id FROM employees").rows)
+    }
+
+    @Test
+    fun rowTriggersFireForEachMergeDrivenAction() {
+        val db = newDatabase()
+        db.run("CREATE TABLE t (id INTEGER PRIMARY KEY, label TEXT)")
+        db.run("CREATE TABLE s (id INTEGER, label TEXT)")
+        db.run("CREATE TABLE log (event TEXT)")
+        db.run("INSERT INTO t VALUES (1, 'old'), (2, 'gone')")
+        db.run("INSERT INTO s VALUES (1, 'new'), (2, 'new'), (3, 'fresh')")
+        db.run("CREATE TRIGGER log_insert AFTER INSERT ON t FOR EACH ROW BEGIN INSERT INTO log VALUES (CONCAT('insert:', NEW.label)); END")
+        db.run("CREATE TRIGGER log_update AFTER UPDATE ON t FOR EACH ROW BEGIN INSERT INTO log VALUES (CONCAT('update:', NEW.label)); END")
+        db.run("CREATE TRIGGER log_delete AFTER DELETE ON t FOR EACH ROW BEGIN INSERT INTO log VALUES (CONCAT('delete:', OLD.label)); END")
+        db.exec(
+            "MERGE INTO t USING s ON t.id = s.id " +
+                "WHEN MATCHED AND s.id = 2 THEN DELETE " +
+                "WHEN MATCHED THEN UPDATE SET label = s.label " +
+                "WHEN NOT MATCHED THEN INSERT (id, label) VALUES (s.id, s.label)"
+        )
+        assertEquals(
+            setOf(text("update:new"), text("delete:gone"), text("insert:fresh")),
+            db.select("SELECT event FROM log").rows.map { it.single() }.toSet()
+        )
+    }
+
+    @Test
+    fun rollingBackATransactionUndoesEveryEffectOfAMerge() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 50), (2, 20)")
+        db.run("BEGIN")
+        db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = accounts.balance + staging.amount " +
+                "WHEN NOT MATCHED THEN INSERT (id, balance) VALUES (staging.id, staging.amount)"
+        )
+        db.run("ROLLBACK")
+        assertEquals(listOf(listOf(int(1), int(100))), db.select("SELECT id, balance FROM accounts").rows)
+    }
+
+    @Test
+    fun anAliasedTargetAndSourceCanBeReferencedByTheirAlias() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 25)")
+        db.exec(
+            "MERGE INTO accounts AS acc USING staging AS s ON acc.id = s.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = acc.balance + s.amount"
+        )
+        assertEquals(listOf(listOf(int(125))), db.select("SELECT balance FROM accounts").rows)
+    }
+
+    @Test
+    fun mergeRequiresAtLeastOneWhenClause() {
+        val db = newDatabase()
+        db.run("CREATE TABLE t (id INTEGER PRIMARY KEY)")
+        db.run("CREATE TABLE s (id INTEGER)")
+        assertFailsWith<KestrelException> { db.run("MERGE INTO t USING s ON t.id = s.id") }
+    }
+
+    @Test
+    fun mergingIntoAnUnknownTableFails() {
+        val db = newDatabase()
+        db.run("CREATE TABLE s (id INTEGER)")
+        assertFailsWith<KestrelException> {
+            db.run("MERGE INTO nope USING s ON nope.id = s.id WHEN MATCHED THEN DELETE")
+        }
+    }
+
+    @Test
+    fun mergeSurvivesClosingAndReopeningTheCatalog() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 50), (2, 20)")
+        db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = accounts.balance + staging.amount " +
+                "WHEN NOT MATCHED THEN INSERT (id, balance) VALUES (staging.id, staging.amount)"
+        )
+        db.reopen()
+        assertEquals(
+            listOf(listOf(int(1), int(150)), listOf(int(2), int(20))),
+            db.select("SELECT id, balance FROM accounts ORDER BY id").rows
+        )
+    }
+
+    @Test
+    fun returningStarProjectsEveryColumnOfEveryActionedRow() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 10), (2, 5)")
+        val result = db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = accounts.balance + staging.amount " +
+                "WHEN NOT MATCHED THEN INSERT (id, balance) VALUES (staging.id, staging.amount) " +
+                "RETURNING *"
+        ) as MergeResult
+        assertEquals(listOf("id", "balance"), result.returning!!.columns)
+        assertEquals(
+            listOf(listOf(int(1), int(110)), listOf(int(2), int(5))),
+            result.returning!!.rows
+        )
+    }
+
+    @Test
+    fun returningEvaluatesExpressionsAgainstTheAffectedRow() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 10)")
+        val result = db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = accounts.balance + staging.amount " +
+                "RETURNING balance * 2 AS doubled"
+        ) as MergeResult
+        assertEquals(listOf("doubled"), result.returning!!.columns)
+        assertEquals(listOf(listOf(int(220))), result.returning!!.rows)
+    }
+
+    @Test
+    fun returningIncludesThePreDeletionImageOfADeletedRow() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 0)")
+        val result = db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id WHEN MATCHED THEN DELETE RETURNING id, balance"
+        ) as MergeResult
+        assertEquals(listOf(listOf(int(1), int(100))), result.returning!!.rows)
+        assertEquals(emptyList(), db.select("SELECT * FROM accounts").rows)
+    }
+
+    @Test
+    fun mergeActionLabelsEachReturnedRowByWhichClauseFired() {
+        val db = newDatabase()
+        db.run("CREATE TABLE t (id INTEGER PRIMARY KEY, label TEXT)")
+        db.run("CREATE TABLE s (id INTEGER, label TEXT)")
+        db.run("INSERT INTO t VALUES (1, 'old'), (2, 'gone')")
+        db.run("INSERT INTO s VALUES (1, 'new'), (2, 'new'), (3, 'fresh')")
+        val result = db.exec(
+            "MERGE INTO t USING s ON t.id = s.id " +
+                "WHEN MATCHED AND s.id = 2 THEN DELETE " +
+                "WHEN MATCHED THEN UPDATE SET label = s.label " +
+                "WHEN NOT MATCHED THEN INSERT (id, label) VALUES (s.id, s.label) " +
+                "RETURNING id, MERGE_ACTION() AS kind"
+        ) as MergeResult
+        assertEquals(
+            setOf(listOf(int(1), text("UPDATE")), listOf(int(2), text("DELETE")), listOf(int(3), text("INSERT"))),
+            result.returning!!.rows.toSet()
+        )
+    }
+
+    @Test
+    fun noRowMatchingAnyClauseReturnsAnEmptyReturningResultNotANullOne() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 5)")
+        val result = db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED AND staging.amount > 1000 THEN UPDATE SET balance = 0 " +
+                "RETURNING *"
+        ) as MergeResult
+        assertEquals(emptyList(), result.returning!!.rows)
+    }
+
+    @Test
+    fun mergeActionIsRejectedOutsideOfAMergesOwnReturningClause() {
+        val db = newDatabase()
+        db.run("CREATE TABLE t (id INTEGER PRIMARY KEY)")
+        db.run("INSERT INTO t VALUES (1)")
+        val error = assertFailsWith<KestrelException> { db.select("SELECT MERGE_ACTION() FROM t") }
+        assertTrue(error.message!!.contains("MERGE_ACTION"), error.message)
+    }
+
+    @Test
+    fun returningColumnValidationRunsUpFrontEvenWhenNoSourceRowEverReachesAMatchingClause() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        val error = assertFailsWith<KestrelException> {
+            db.run(
+                "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                    "WHEN MATCHED THEN DELETE RETURNING nope"
+            )
+        }
+        assertTrue(error.message!!.contains("no such column"), error.message)
+    }
+
+    @Test
+    fun returningSurvivesClosingAndReopeningTheCatalog() {
+        val db = newDatabase()
+        db.setUpAccountsAndStaging()
+        db.run("INSERT INTO accounts VALUES (1, 100)")
+        db.run("INSERT INTO staging VALUES (1, 50)")
+        val beforeReopen = db.exec(
+            "MERGE INTO accounts USING staging ON accounts.id = staging.id " +
+                "WHEN MATCHED THEN UPDATE SET balance = accounts.balance + staging.amount " +
+                "RETURNING id, balance"
+        ) as MergeResult
+        assertEquals(listOf(listOf(int(1), int(150))), beforeReopen.returning!!.rows)
+        db.reopen()
+        assertEquals(listOf(listOf(int(1), int(150))), db.select("SELECT id, balance FROM accounts").rows)
+    }
+}