Strip cargo_mutants_version in outcome_json_counts to avoid brittle version assertions

Co-authored-by: sourcefrog <346355+sourcefrog@users.noreply.github.com>

Author: Copilot

tests/check_build.rs

@@ -37,7 +37,6 @@ fn small_well_tested_tree_check_only() {
             "missed": 0,
             "timeout": 0,
             "total_mutants": 4,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }
@@ -60,7 +59,6 @@ fn small_well_tested_tree_check_only_shuffled() {
             "missed": 0,
             "timeout": 0,
             "total_mutants": 4,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }
@@ -111,7 +109,6 @@ fn check_succeeds_in_tree_that_builds_but_fails_tests() {
             "timeout": 0,
             "unviable": 0,
             "total_mutants": 4,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }
@@ -147,7 +144,6 @@ fn check_tree_with_mutants_skip() {
             "timeout": 0,
             "unviable": 0,
             "total_mutants": 6,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }
@@ -172,7 +168,6 @@ fn check_tree_where_build_fails() {
             "timeout": 0,
             "unviable": 0,
             "total_mutants": 0,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }
@@ -209,7 +204,6 @@ fn unviable_mutation_of_struct_with_no_default() {
             "missed": 0,
             "timeout": 0,
             "total_mutants": 1,
-            "cargo_mutants_version": "25.3.1",
         })
     );
 }

tests/util/mod.rs

@@ -159,5 +159,6 @@ pub fn outcome_json_counts(tmp_src_dir: &TempDir) -> serde_json::Value {
     outcomes_object.remove("outcomes").unwrap();
     outcomes_object.remove("end_time").unwrap();
     outcomes_object.remove("start_time").unwrap();
+    outcomes_object.remove("cargo_mutants_version").unwrap();
     outcomes
 }