test(lockfile): default lockfile version is still v3

It will become v4 when we changes the default.

tests/testsuite/lockfile_compat.rs

@@ -1175,6 +1175,26 @@ fn v4_and_git_url_encoded_rev() {
 #[cargo_test]
 fn with_msrv() {
     let cksum = Package::new("bar", "0.1.0").publish();
+
+    let v3_lockfile = format!(
+        r#"# This file is automatically @generated by Cargo.
+# It is not intended for manual editing.
+version = 3
+
+[[package]]
+name = "bar"
+version = "0.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "{cksum}"
+
+[[package]]
+name = "foo"
+version = "0.0.1"
+dependencies = [
+ "bar",
+]
+"#
+    );
     let v2_lockfile = format!(
         r#"# This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
@@ -1258,6 +1278,14 @@ dependencies = [
         ("1.53", Some(4), 4),
         // v4 introduced
         ("1.78", None, 3),
+        // last version of v3 as the default
+        ("1.82", None, 3),
+        // v4 is the default
+        ("1.83", None, 3),
+        ("1.83", Some(1), 1),
+        ("1.83", Some(2), 2),
+        ("1.83", Some(3), 3),
+        ("1.83", Some(4), 4),
     ];
 
     for (msrv, existing_lockfile, expected_version) in cases {
@@ -1284,6 +1312,7 @@ dependencies = [
             let existing_lockfile = match existing_lockfile {
                 1 => v1_lockfile.as_str().into(),
                 2 => v2_lockfile.as_str().into(),
+                3 => v3_lockfile.as_str().into(),
                 v => std::borrow::Cow::from(format!("version = {v}")),
             };
             p.change_file("Cargo.lock", &existing_lockfile);