diff --git a/lib/common/test/unit-tests/services/files-hash-service.ts b/lib/common/test/unit-tests/services/files-hash-service.ts
new file mode 100644
index 0000000000..2dd6134232
--- /dev/null
+++ b/lib/common/test/unit-tests/services/files-hash-service.ts
@@ -0,0 +1,103 @@
+import { Yok } from "../../../yok";
+import { FilesHashService } from "../../../../services/files-hash-service";
+import { FileSystemStub, LoggerStub } from "../../../../../test/stubs";
+import { assert } from "chai";
+
+const fileHashes = {
+	"file1": "hash1",
+	"file2": "hash2",
+	"file3": "hash3",
+	"file4": "hash4",
+	"file5": "hash5",
+	"file6": "hash6",
+	"file7": "hash7"
+};
+
+function createTestInjector(): IInjector {
+	const injector = new Yok();
+	injector.register("fs", FileSystemStub);
+	injector.register("logger", LoggerStub);
+	injector.register("filesHashService", FilesHashService);
+
+	return injector;
+}
+
+function addFileHashes(hashes: IStringDictionary) {
+	const result = {};
+	_.extend(result, fileHashes, hashes);
+	return result;
+}
+
+function removeFileHashes(hashes: IStringDictionary) {
+	const result = _.omitBy(fileHashes, (hash: string, filePath: string) => !!_.find(hashes, (newHash: string, newFilePath: string) => newHash === hash && newFilePath === filePath));
+	return result;
+}
+
+function mockFilesHashService(hashes: IStringDictionary): IFilesHashService {
+	const injector = createTestInjector();
+	const filesHashService = injector.resolve("filesHashService");
+	filesHashService.generateHashes = async () => hashes;
+
+	return filesHashService;
+}
+
+describe("filesHashService", () => {
+	const testCases = [
+		{
+			name: "should not return changes when no files are changed",
+			newHashes: fileHashes,
+			oldHashes: fileHashes,
+			expectedChanges: {}
+		},
+		{
+			name: "should return changes when a file is added",
+			newHashes: addFileHashes({ "file8": "hash8" }),
+			oldHashes: fileHashes,
+			expectedChanges: { "file8": "hash8" }
+		},
+		{
+			name: "should return changes when a file is removed",
+			newHashes: removeFileHashes({ "file7": "hash7" }),
+			oldHashes: fileHashes,
+			expectedChanges: { "file7": "hash7" }
+		},
+		{
+			name: "should return changes when a file is added and a file is removed from oldHashes",
+			newHashes: addFileHashes({ "file9": "hash9" }),
+			oldHashes: removeFileHashes({ "file1": "hash1" }),
+			expectedChanges: { "file1": "hash1", "file9": "hash9" }
+		},
+		{
+			name: "should return changes when no oldHashes are provided",
+			newHashes: fileHashes,
+			oldHashes: {},
+			expectedChanges: fileHashes
+		},
+		{
+			name: "should return changes when no newHashes are provided",
+			newHashes: {},
+			oldHashes: fileHashes,
+			expectedChanges: fileHashes
+		}
+	];
+
+	describe("getChanges", () => {
+		_.each(testCases, (testCase: any) => {
+			it(`${testCase.name}`, async () => {
+				const filesHashService = mockFilesHashService(testCase.newHashes);
+				const changes = await filesHashService.getChanges(_.keys(testCase.newHashes), testCase.oldHashes);
+				assert.deepEqual(changes, testCase.expectedChanges);
+			});
+		});
+	});
+
+	describe("hasChangesInShasums", () => {
+		_.each(testCases, (testCase: any) => {
+			it(`${testCase.name}`, () => {
+				const filesHashService = mockFilesHashService(testCase.newHashes);
+				const hasChanges = filesHashService.hasChangesInShasums(testCase.newHashes, testCase.oldHashes);
+				assert.deepEqual(hasChanges, !!_.keys(testCase.expectedChanges).length);
+			});
+		});
+	});
+});
diff --git a/lib/services/files-hash-service.ts b/lib/services/files-hash-service.ts
index f8893e4d99..3efb780d2c 100644
--- a/lib/services/files-hash-service.ts
+++ b/lib/services/files-hash-service.ts
@@ -53,8 +53,13 @@ export class FilesHashService implements IFilesHashService {
 		this.$fs.writeJson(hashesFilePath, hashes);
 	}
 
-	private getChangesInShasums(oldHashes: IStringDictionary, newHashes: IStringDictionary): IStringDictionary {
-		return _.omitBy(newHashes, (hash: string, pathToFile: string) => !!_.find(oldHashes, (oldHash: string, oldPath: string) => pathToFile === oldPath && hash === oldHash));
+	public getChangesInShasums(oldHashes: IStringDictionary, newHashes: IStringDictionary): IStringDictionary {
+		const addedFileHashes = _.omitBy(newHashes, (hash: string, pathToFile: string) => !!oldHashes[pathToFile] && oldHashes[pathToFile] === hash);
+		const removedFileHashes = _.omitBy(oldHashes, (hash: string, pathToFile: string) => !!newHashes[pathToFile] && newHashes[pathToFile] === hash);
+		const result = {};
+		_.extend(result, addedFileHashes, removedFileHashes);
+
+		return result;
 	}
 }
 $injector.register("filesHashService", FilesHashService);