Factor test tools between store and fragment

Those need the driver to deal with the fact that the store is stateful. Those
tests can't be moved to the test suite because they use private functions.

libraries/persistent_store/src/store.rs

@@ -1301,71 +1301,15 @@ fn is_write_needed(source: &[u8], target: &[u8]) -> StoreResult<bool> {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::BufferOptions;
-
-    #[derive(Clone)]
-    struct Config {
-        word_size: usize,
-        page_size: usize,
-        num_pages: usize,
-        max_word_writes: usize,
-        max_page_erases: usize,
-    }
-
-    impl Config {
-        fn new_driver(&self) -> StoreDriverOff {
-            let options = BufferOptions {
-                word_size: self.word_size,
-                page_size: self.page_size,
-                max_word_writes: self.max_word_writes,
-                max_page_erases: self.max_page_erases,
-                strict_mode: true,
-            };
-            StoreDriverOff::new(options, self.num_pages)
-        }
-    }
-
-    const MINIMAL: Config = Config {
-        word_size: 4,
-        page_size: 64,
-        num_pages: 5,
-        max_word_writes: 2,
-        max_page_erases: 9,
-    };
-
-    const NORDIC: Config = Config {
-        word_size: 4,
-        page_size: 0x1000,
-        num_pages: 20,
-        max_word_writes: 2,
-        max_page_erases: 10000,
-    };
-
-    const TITAN: Config = Config {
-        word_size: 4,
-        page_size: 0x800,
-        num_pages: 10,
-        max_word_writes: 2,
-        max_page_erases: 10000,
-    };
+    use crate::test::MINIMAL;
 
     #[test]
-    fn nordic_capacity() {
-        let driver = NORDIC.new_driver().power_on().unwrap();
-        assert_eq!(driver.model().capacity().total, 19123);
-    }
-
-    #[test]
-    fn titan_capacity() {
-        let driver = TITAN.new_driver().power_on().unwrap();
-        assert_eq!(driver.model().capacity().total, 4315);
-    }
-
-    #[test]
-    fn minimal_virt_page_size() {
-        // Make sure a virtual page has 14 words. We use this property in the other tests below to
-        // know whether entries are spanning, starting, and ending pages.
-        assert_eq!(MINIMAL.new_driver().model().format().virt_page_size(), 14);
+    fn is_write_needed_ok() {
+        assert_eq!(is_write_needed(&[], &[]), Ok(false));
+        assert_eq!(is_write_needed(&[0], &[0]), Ok(false));
+        assert_eq!(is_write_needed(&[0], &[1]), Err(StoreError::InvalidStorage));
+        assert_eq!(is_write_needed(&[1], &[0]), Ok(true));
+        assert_eq!(is_write_needed(&[1], &[1]), Ok(false));
     }
 
     #[test]