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diff --git a/jstests/multiVersion/426_wt_log_version.js b/jstests/multiVersion/426_wt_log_version.js
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+++ b/jstests/multiVersion/426_wt_log_version.js
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+/**
+ * 4.2.6+ has the following capabilities:
+ * - It can read data left behind by 4.4.
+ * - It can read data left behind by 4.2.5-
+ * - It can read/write log version 3 (used by 4.2.5-)
+ * - It can read/write log version 4 (only known by 4.2.6+)
+ *
+ * This test ensures that a 4.2.5- ("4.2 classic") version can binary upgrade to 4.2.6+ and
+ * binary downgrade back to a 4.2 classic version.
+ *
+ * This test ensures that a clean database started on a 4.2.6+ binary can binary downgrade to a 4.2
+ * classic version.
+ */
+(function() {
+"use strict";
+// Chosen only because other multiversion tests target 4.2.1.
+const classic42 = "4.2.1";
+
+// Test the following binary version changes succeeds: classic -> 4.2.6+ -> classic
+{
+    let conn = MongoRunner.runMongod({cleanData: true, binVersion: classic42});
+    assert.neq(null, conn, "mongod-" + classic42 + " failed to start up");
+    MongoRunner.stopMongod(conn);
+
+    conn = MongoRunner.runMongod({restart: conn, noCleanData: true, binVersion: "4.2"});
+    assert.neq(null, conn, "mongod-4.2-latest failed to start up");
+    MongoRunner.stopMongod(conn);
+
+    conn = MongoRunner.runMongod({restart: conn, noCleanData: true, binVersion: classic42});
+    assert.neq(null, conn, "mongod-" + classic42 + " failed to start up after 4.2 shutdown");
+    MongoRunner.stopMongod(conn);
+}
+
+// Test that a new dbpath on 4.2.6+ can binary downgrade to 4.2 classic.
+{
+    let conn = MongoRunner.runMongod({cleanData: true, binVersion: "4.2"});
+    assert.neq(null, conn, "mongod-4.2-latest failed to start up");
+    MongoRunner.stopMongod(conn);
+
+    conn = MongoRunner.runMongod({restart: conn, noCleanData: true, binVersion: classic42});
+    assert.neq(null, conn, "mongod-" + classic42 + " failed to start up");
+    MongoRunner.stopMongod(conn);
+}
+})();