Generate more comparison operator mutant variants

NEWS.md

@@ -2,6 +2,8 @@
 
 ## Unreleased
 
+- New: Generate more comparison operator mutant variants: `<` and `>` now also mutate to `>=` and `<=` respectively as a way of negating the condition, and `<=` and `>=` now mutate to `<` and `>` as well to catch off-by-one errors.
+
 - New: `#[mutants::exclude_re("pattern")]` attribute to exclude specific mutations by regex, without disabling all mutations on the function. The attribute can be placed on functions, `impl` blocks, `trait` blocks, modules, files, and on expressions that can carry an attribute (such as `match`, struct literals, call expressions, method calls, and unary expressions). Multiple patterns can be applied. Also supported within `cfg_attr`. Requires the [mutants](https://crates.io/crates/mutants) crate version `0.0.5` or later.
 
 - Fixed: `#[mutants::skip]` (and `#[cfg_attr(..., mutants::skip)]`) is now honoured when placed on `const` and `static` items, including associated constants in `impl` and `trait` blocks. Previously the attribute was silently ignored on these items and operator mutants inside the initializer expression were still generated ([#508](https://github.com/sourcefrog/cargo-mutants/issues/508)).

book/src/mutants.md

@@ -81,10 +81,10 @@ like `a == 0`.
 | `!=`     | `==`               |
 | `&&`     | `\|\|`             |
 | `\|\|`   | `&&`,              |
-| `<`      | `==`, `>`          |
-| `>`      | `==`, `<`          |
-| `<=`     | `>`                |
-| `>=`     | `<`                |
+| `<`      | `==`, `>`, `<=`, `>=` |
+| `>`      | `==`, `<`, `>=`, `<=` |
+| `<=`     | `<`, `>`           |
+| `>=`     | `>`, `<`           |
 | `+`      | `-`, `*`           |
 | `-`      | `+`, `/`           |
 | `*`      | `+`, `/`           |

src/mutant.rs

@@ -477,6 +477,7 @@ mod test {
                 "replace > with == in controlled_loop",
                 "replace > with < in controlled_loop",
                 "replace > with >= in controlled_loop",
+                "replace > with <= in controlled_loop",
                 "replace * with + in controlled_loop",
                 "replace * with / in controlled_loop",
             ]

src/visit.rs

@@ -799,10 +799,10 @@ impl<'ast> Visit<'ast> for DiscoveryVisitor<'_> {
             BinOp::Ne(_) => vec![quote! { == }],
             BinOp::And(_) => vec![quote! { || }],
             BinOp::Or(_) => vec![quote! { && }],
-            BinOp::Lt(_) => vec![quote! { == }, quote! {>}, quote! { <= }],
-            BinOp::Gt(_) => vec![quote! { == }, quote! {<}, quote! { >= }],
-            BinOp::Le(_) => vec![quote! {>}],
-            BinOp::Ge(_) => vec![quote! {<}],
+            BinOp::Lt(_) => vec![quote! { == }, quote! {>}, quote! { <= }, quote! { >= }],
+            BinOp::Gt(_) => vec![quote! { == }, quote! {<}, quote! { >= }, quote! { <= }],
+            BinOp::Le(_) => vec![quote! {<}, quote! {>}],
+            BinOp::Ge(_) => vec![quote! {>}, quote! {<}],
             BinOp::Add(_) => vec![quote! {-}, quote! {*}],
             BinOp::AddAssign(_) => vec![quote! {-=}, quote! {*=}],
             BinOp::Sub(_) | BinOp::Mul(_) => vec![quote! {+}, quote! {/}],
@@ -1821,16 +1821,32 @@ mod test {
     fn mutate_comparisons() {
         assert_eq!(
             mutate_expr("a > b"),
-            &["replace > with ==", "replace > with <", "replace > with >="]
+            &[
+                "replace > with ==",
+                "replace > with <",
+                "replace > with >=",
+                "replace > with <="
+            ]
         );
         assert_eq!(
             mutate_expr("a < b "),
-            &["replace < with ==", "replace < with >", "replace < with <="]
+            &[
+                "replace < with ==",
+                "replace < with >",
+                "replace < with <=",
+                "replace < with >="
+            ]
         );
         assert_eq!(mutate_expr("a == b"), &["replace == with !="]);
         assert_eq!(mutate_expr("a != b"), &["replace != with =="]);
-        assert_eq!(mutate_expr("a >= b"), &["replace >= with <"]);
-        assert_eq!(mutate_expr("a <= b"), &["replace <= with >"]);
+        assert_eq!(
+            mutate_expr("a >= b"),
+            &["replace >= with >", "replace >= with <"]
+        );
+        assert_eq!(
+            mutate_expr("a <= b"),
+            &["replace <= with <", "replace <= with >"]
+        );
     }
 
     #[test]

tests/main.rs

@@ -2605,26 +2605,27 @@ fn check_tree_with_mutants_skip() {
         .assert()
         .success()
         .stdout(indoc! { r"
-            Found 6 mutants to test
+            Found 7 mutants to test
             ok       Unmutated baseline
             ok       src/lib.rs:15:5: replace controlled_loop with ()
             ok       src/lib.rs:21:28: replace > with == in controlled_loop
             ok       src/lib.rs:21:28: replace > with < in controlled_loop
             ok       src/lib.rs:21:28: replace > with >= in controlled_loop
+            ok       src/lib.rs:21:28: replace > with <= in controlled_loop
             ok       src/lib.rs:21:53: replace * with + in controlled_loop
             ok       src/lib.rs:21:53: replace * with / in controlled_loop
-            6 mutants tested: 6 succeeded
+            7 mutants tested: 7 succeeded
             "})
         .stderr("");
     assert_eq!(
         outcome_json_counts(&tmp_src_dir),
         serde_json::json!({
             "caught": 0,
             "missed": 0,
-            "success": 6,
+            "success": 7,
             "timeout": 0,
             "unviable": 0,
-            "total_mutants": 6,
+            "total_mutants": 7,
         })
     );
 }

tests/snapshots/main__cargo_mutants_in_relative_dependency_tree_passes.snap

@@ -1,8 +1,7 @@
 ---
 source: tests/main.rs
 expression: stdout
-snapshot_kind: text
 ---
-Found 7 mutants to test
+Found 8 mutants to test
 ok       Unmutated baseline
-7 mutants tested: 7 caught
+8 mutants tested: 8 caught

tests/util/snapshots/main__util__list_mutants_json_well_tested.snap

@@ -1,8 +1,6 @@
 ---
 source: tests/util/mod.rs
-assertion_line: 33
 expression: "String::from_utf8_lossy(&output.stdout)"
-
 ---
 [
   {
@@ -1893,6 +1891,38 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     }
   },
+  {
+    "diff": "--- src/result.rs\n+++ replace < with >= in error_if_negative\n@@ -2,17 +2,17 @@\n // fn io_result() -> std::io::Result<\n \n /// Simple easily-recognizable Result.\n fn simple_result() -> Result<&'static str, ()> {\n     Ok(\"success\")\n }\n \n fn error_if_negative(a: i32) -> Result<(), ()> {\n-    if a < 0 {\n+    if a >= /* ~ changed by cargo-mutants ~ */ 0 {\n         Err(())\n     } else {\n         Ok(())\n     }\n }\n \n fn result_with_no_apparent_type_args() -> std::fmt::Result {\n     Err(Default::default())\n",
+    "file": "src/result.rs",
+    "function": {
+      "function_name": "error_if_negative",
+      "return_type": "-> Result<(), ()>",
+      "span": {
+        "end": {
+          "column": 2,
+          "line": 15
+        },
+        "start": {
+          "column": 1,
+          "line": 9
+        }
+      }
+    },
+    "genre": "BinaryOperator",
+    "name": "src/result.rs:10:10: replace < with >= in error_if_negative",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": ">=",
+    "span": {
+      "end": {
+        "column": 11,
+        "line": 10
+      },
+      "start": {
+        "column": 10,
+        "line": 10
+      }
+    }
+  },
   {
     "diff": "--- src/result.rs\n+++ replace result_with_no_apparent_type_args -> std::fmt::Result with Ok(Default::default())\n@@ -10,17 +10,17 @@\n     if a < 0 {\n         Err(())\n     } else {\n         Ok(())\n     }\n }\n \n fn result_with_no_apparent_type_args() -> std::fmt::Result {\n-    Err(Default::default())\n+    Ok(Default::default()) /* ~ changed by cargo-mutants ~ */\n }\n \n mod test {\n     use super::*;\n \n     #[test]\n     fn simple_result_success() {\n         assert_eq!(simple_result(), Ok(\"success\"));\n",
     "file": "src/result.rs",
@@ -2661,6 +2691,38 @@ expression: "String::from_utf8_lossy(&output.stdout)"
       }
     }
   },
+  {
+    "diff": "--- src/slices.rs\n+++ replace < with >= in pad\n@@ -1,13 +1,13 @@\n use std::borrow::Cow;\n \n fn pad<'a>(aa: &'a mut [Cow<'static, str>]) -> &'a [Cow<'static, str>] {\n     for a in aa.iter_mut() {\n-        if a.len() < 3 {\n+        if a.len() >= /* ~ changed by cargo-mutants ~ */ 3 {\n             a.to_mut().push_str(\"___\");\n         }\n     }\n     aa\n }\n \n fn return_mut_slice(a: &mut [usize]) -> &mut [usize] {\n     for x in a.iter_mut() {\n",
+    "file": "src/slices.rs",
+    "function": {
+      "function_name": "pad",
+      "return_type": "-> &'a[Cow<'static, str>]",
+      "span": {
+        "end": {
+          "column": 2,
+          "line": 10
+        },
+        "start": {
+          "column": 1,
+          "line": 3
+        }
+      }
+    },
+    "genre": "BinaryOperator",
+    "name": "src/slices.rs:5:20: replace < with >= in pad",
+    "package": "cargo-mutants-testdata-well-tested",
+    "replacement": ">=",
+    "span": {
+      "end": {
+        "column": 21,
+        "line": 5
+      },
+      "start": {
+        "column": 20,
+        "line": 5
+      }
+    }
+  },
   {
     "diff": "--- src/slices.rs\n+++ replace return_mut_slice -> &mut[usize] with Vec::leak(Vec::new())\n@@ -5,20 +5,17 @@\n         if a.len() < 3 {\n             a.to_mut().push_str(\"___\");\n         }\n     }\n     aa\n }\n \n fn return_mut_slice(a: &mut [usize]) -> &mut [usize] {\n-    for x in a.iter_mut() {\n-        *x *= 2\n-    }\n-    a\n+    Vec::leak(Vec::new()) /* ~ changed by cargo-mutants ~ */\n }\n \n #[cfg(test)]\n mod test {\n     #[test]\n     fn test_pad() {\n         assert_eq!(\n             super::pad(&mut [\"hello\".into(), \"ok\".into(), \"cat\".into()]),\n",
     "file": "src/slices.rs",

tests/util/snapshots/main__util__list_mutants_well_tested.snap

@@ -61,6 +61,7 @@ src/result.rs:10:5: replace error_if_negative -> Result<(), ()> with Ok(())
 src/result.rs:10:10: replace < with == in error_if_negative
 src/result.rs:10:10: replace < with > in error_if_negative
 src/result.rs:10:10: replace < with <= in error_if_negative
+src/result.rs:10:10: replace < with >= in error_if_negative
 src/result.rs:18:5: replace result_with_no_apparent_type_args -> std::fmt::Result with Ok(Default::default())
 src/sets.rs:4:5: replace make_a_set -> BTreeSet<String> with BTreeSet::new()
 src/sets.rs:4:5: replace make_a_set -> BTreeSet<String> with BTreeSet::from_iter([String::new()])
@@ -85,6 +86,7 @@ src/slices.rs:4:5: replace pad -> &'a[Cow<'static, str>] with Vec::leak(vec![Cow
 src/slices.rs:5:20: replace < with == in pad
 src/slices.rs:5:20: replace < with > in pad
 src/slices.rs:5:20: replace < with <= in pad
+src/slices.rs:5:20: replace < with >= in pad
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(Vec::new())
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![0])
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![1])

tests/util/snapshots/main__util__list_mutants_well_tested_exclude_name_filter.snap

@@ -61,6 +61,7 @@ src/result.rs:10:5: replace error_if_negative -> Result<(), ()> with Ok(())
 src/result.rs:10:10: replace < with == in error_if_negative
 src/result.rs:10:10: replace < with > in error_if_negative
 src/result.rs:10:10: replace < with <= in error_if_negative
+src/result.rs:10:10: replace < with >= in error_if_negative
 src/result.rs:18:5: replace result_with_no_apparent_type_args -> std::fmt::Result with Ok(Default::default())
 src/sets.rs:4:5: replace make_a_set -> BTreeSet<String> with BTreeSet::new()
 src/sets.rs:4:5: replace make_a_set -> BTreeSet<String> with BTreeSet::from_iter([String::new()])
@@ -73,6 +74,7 @@ src/slices.rs:4:5: replace pad -> &'a[Cow<'static, str>] with Vec::leak(vec![Cow
 src/slices.rs:5:20: replace < with == in pad
 src/slices.rs:5:20: replace < with > in pad
 src/slices.rs:5:20: replace < with <= in pad
+src/slices.rs:5:20: replace < with >= in pad
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(Vec::new())
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![0])
 src/slices.rs:13:5: replace return_mut_slice -> &mut[usize] with Vec::leak(vec![1])