Add test for disk I/O usage

Cargo.toml

@@ -117,6 +117,7 @@ procfs = "0.17.0"
 [dev-dependencies]
 serde_json = "1.0" # Used in documentation tests.
 bstr = "1.9.0"
+tempfile = "3.9"
 
 [[example]]
 name = "simple"

tests/disk.rs

@@ -0,0 +1,62 @@
+// Take a look at the license at the top of the repository in the LICENSE file.
+
+#[test]
+#[cfg(all(feature = "system", feature = "disk"))]
+fn test_disks() {
+    if sysinfo::IS_SUPPORTED_SYSTEM {
+        let s = sysinfo::System::new_all();
+        // If we don't have any physical core present, it's very likely that we're inside a VM...
+        if s.physical_core_count().unwrap_or_default() > 0 {
+            let mut disks = sysinfo::Disks::new();
+            assert!(disks.list().is_empty());
+            disks.refresh_list();
+            assert!(!disks.list().is_empty());
+        }
+    }
+}
+
+#[test]
+#[cfg(feature = "disk")]
+fn test_disks_usage() {
+    use std::io::Write;
+    use tempfile::NamedTempFile;
+
+    if !sysinfo::IS_SUPPORTED_SYSTEM {
+        return;
+    }
+
+    let mut disks = sysinfo::Disks::new_with_refreshed_list();
+
+    let mut file = NamedTempFile::new().unwrap();
+
+    // Writes 10mb worth of data to the temp file
+    let size = 10 * 1024 * 1024;
+    let data = vec![0u8; size];
+    file.write_all(&data).unwrap();
+    file.flush().unwrap();
+
+    // Read data back from the temp file
+    let _ = std::fs::read(file.path()).unwrap();
+
+    // Wait a bit before refreshing the disk usage stats
+    std::thread::sleep(std::time::Duration::from_millis(500));
+    disks.refresh();
+
+    // Depending on the OS and how disks are configured, the disk usage may be the exact same
+    // across multiple disks. To account for this, collect the disk usages and dedup
+    let mut disk_usages = disks.list().iter().map(|d| d.usage()).collect::<Vec<_>>();
+    disk_usages.dedup();
+
+    let mut read_bytes = 0;
+    let mut written_bytes = 0;
+    for disk_usage in disk_usages {
+        read_bytes += disk_usage.read_bytes;
+        written_bytes += disk_usage.written_bytes;
+    }
+
+    // We expect written_bytes to have increased by about 10mb but due to unknown reasons, it is sometimes
+    // less than 10mb. Settle in the middle with at least 5mb increase
+    assert!(written_bytes >= 5 * 1024 * 1024);
+    // Validating read_bytes is not as straightforward due to caching. We'll settle for any amount of increase.
+    assert!(read_bytes > 0);
+}