make corrections to the test

Author: JustForFun88

src/map.rs

@@ -8045,31 +8045,35 @@ mod test_map {
         use crate::TryReserveError::{AllocError, CapacityOverflow};
 
         const MAX_ISIZE: usize = isize::MAX as usize;
+        const GROUP_WIDTH: usize = 128;
 
         let mut empty_bytes: HashMap<u8, u8> = HashMap::new();
 
         if let Err(CapacityOverflow) = empty_bytes.try_reserve(usize::MAX) {
         } else {
-            panic!("usize::MAX should trigger an overflow!");
+            panic!("isize::MAX should trigger an overflow!");
         }
 
         if let Err(CapacityOverflow) = empty_bytes.try_reserve(MAX_ISIZE) {
         } else {
-            panic!("usize::MAX should trigger an overflow!");
+            panic!("isize::MAX should trigger an overflow!");
         }
 
-        if let Err(AllocError { .. }) = empty_bytes.try_reserve(MAX_ISIZE / 16) {
+        if let Err(AllocError { .. }) = empty_bytes.try_reserve(MAX_ISIZE / 24 - (GROUP_WIDTH + 1))
+        {
         } else {
             // This may succeed if there is enough free memory. Attempt to
             // allocate a few more hashmaps to ensure the allocation will fail.
             let mut empty_bytes2: HashMap<u8, u8> = HashMap::new();
-            let _ = empty_bytes2.try_reserve(MAX_ISIZE / 16);
+            let _ = empty_bytes2.try_reserve(MAX_ISIZE / 24 - (GROUP_WIDTH + 1));
             let mut empty_bytes3: HashMap<u8, u8> = HashMap::new();
-            let _ = empty_bytes3.try_reserve(MAX_ISIZE / 16);
+            let _ = empty_bytes3.try_reserve(MAX_ISIZE / 24 - (GROUP_WIDTH + 1));
             let mut empty_bytes4: HashMap<u8, u8> = HashMap::new();
-            if let Err(AllocError { .. }) = empty_bytes4.try_reserve(MAX_ISIZE / 16) {
+            if let Err(AllocError { .. }) =
+                empty_bytes4.try_reserve(MAX_ISIZE / 24 - (GROUP_WIDTH + 1))
+            {
             } else {
-                panic!("usize::MAX / 8 should trigger an OOM!");
+                panic!("isize::MAX / 24 should trigger an OOM!");
             }
         }
     }