Adding blob tests (#3719)

provider/blob/src/blob_data_provider.rs

@@ -136,3 +136,79 @@ impl BufferProvider for BlobDataProvider {
         })
     }
 }
+
+#[cfg(test)]
+mod test {
+    use super::*;
+    use crate::export::*;
+    use icu_provider::datagen::*;
+    use icu_provider::hello_world::*;
+
+    #[icu_provider::data_struct(marker(HelloSingletonV1Marker, "hello/singleton@1", singleton))]
+    #[derive(Clone, Copy)]
+    pub struct HelloSingletonV1;
+
+    #[test]
+    fn test_empty() {
+        let mut blob: Vec<u8> = Vec::new();
+
+        {
+            let mut exporter = BlobExporter::new_with_sink(Box::new(&mut blob));
+
+            exporter
+                .flush_with_fallback(HelloWorldV1Marker::KEY, FallbackMode::None)
+                .unwrap();
+
+            exporter.close().unwrap();
+        }
+
+        let provider = BlobDataProvider::try_new_from_blob(blob.into()).unwrap();
+
+        assert!(matches!(
+            provider.load_buffer(HelloWorldV1Marker::KEY, Default::default()),
+            Err(DataError {
+                kind: DataErrorKind::MissingLocale,
+                ..
+            })
+        ));
+    }
+
+    #[test]
+    fn test_singleton() {
+        let mut blob: Vec<u8> = Vec::new();
+
+        {
+            let mut exporter = BlobExporter::new_with_sink(Box::new(&mut blob));
+
+            exporter
+                .flush_with_fallback(HelloSingletonV1Marker::KEY, FallbackMode::None)
+                .unwrap();
+
+            exporter.close().unwrap();
+        }
+
+        let provider = BlobDataProvider::try_new_from_blob(blob.into()).unwrap();
+
+        assert!(matches!(
+            provider.load_buffer(
+                HelloSingletonV1Marker::KEY,
+                DataRequest {
+                    locale: &icu_locid::locale!("de").into(),
+                    metadata: Default::default()
+                }
+            ),
+            Err(DataError {
+                kind: DataErrorKind::ExtraneousLocale,
+                ..
+            })
+        ));
+
+        assert!(matches!(
+            provider.load_buffer(HelloSingletonV1Marker::KEY, Default::default()),
+            Err(DataError {
+                kind: DataErrorKind::MissingLocale,
+                ..
+            })
+        ));
+    }
+}

provider/blob/src/blob_schema.rs

@@ -81,7 +81,7 @@ impl<'data> BlobSchemaV1<'data> {
         // Note: We could check that every index occurs at least once, but that's a more expensive
         // operation, so we will just check for the min and max index.
         let mut seen_min = false;
-        let mut seen_max = false;
+        let mut seen_max = self.buffers.is_empty();
         for cursor in self.keys.iter0() {
             for (locale, idx) in cursor.iter1_copied() {
                 debug_assert!(idx < self.buffers.len() || locale == Index32U8::SENTINEL);