acpi_tables: Add test case for reading SDT data from files

Seemed like an easy test to add.

BUG=b:171082843
TEST=This is a test

Change-Id: I2a10c0965be2952cd3150965e4127a27a3ec6dff
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/crosvm/+/2495844
Reviewed-by: Tomasz Jeznach <tjeznach@chromium.org>
Commit-Queue: Dennis Kempin <denniskempin@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Auto-Submit: Dennis Kempin <denniskempin@google.com>

Cargo.lock

@@ -26,6 +26,7 @@ name = "acpi_tables"
 version = "0.1.0"
 dependencies = [
  "data_model 0.1.0",
+ "tempfile 3.0.7",
 ]
 
 [[package]]

acpi_tables/Cargo.toml

@@ -6,3 +6,4 @@ edition = "2018"
 
 [dependencies]
 data_model = { path = "../data_model" }
+tempfile = { path = "../tempfile" }

acpi_tables/src/sdt.rs

@@ -114,6 +114,8 @@ impl SDT {
 #[cfg(test)]
 mod tests {
     use super::SDT;
+    use std::io::Write;
+    use tempfile::NamedTempFile;
 
     #[test]
     fn test_sdt() {
@@ -130,4 +132,22 @@ mod tests {
             .fold(0u8, |acc, x| acc.wrapping_add(*x));
         assert_eq!(sum, 0);
     }
+
+    #[test]
+    fn test_sdt_read_write() -> Result<(), std::io::Error> {
+        let temp_file = NamedTempFile::new()?;
+        let expected_sdt = SDT::new(*b"TEST", 40, 1, *b"CROSVM", *b"TESTTEST", 1);
+
+        // Write SDT to file.
+        {
+            let mut writer = temp_file.as_file();
+            writer.write_all(&expected_sdt.as_slice())?;
+        }
+
+        // Read it back and verify.
+        let actual_sdt = SDT::from_file(&temp_file.path().to_path_buf())?;
+        assert!(actual_sdt.is_signature(b"TEST"));
+        assert_eq!(actual_sdt.as_slice(), expected_sdt.as_slice());
+        Ok(())
+    }
 }