test: update/create tests

jest.config.js

@@ -0,0 +1,9 @@
+/**
+ * @type {import('jest').Config}
+ */
+module.exports = {
+  preset: 'ts-jest',
+  testEnvironment: 'node',
+  testPathIgnorePatterns: ['/node_modules/', '/dist/', '/tests/__mocks__'],
+  coveragePathIgnorePatterns: ['./src/index.ts'],
+}

tests/__mocks__/mockFileReader.ts

@@ -0,0 +1,20 @@
+global.window = {
+  // @ts-ignore
+  FileReader: class MockFileReader {
+    onload: any = null
+    onerror: any = null
+    result = ''
+
+    async readAsText(blob: Blob) {
+      try {
+        if (blob instanceof Blob) {
+          const result = await blob.text()
+          this.onload({ target: { result } })
+        } else
+          this.onerror({ target: { error: new DOMException('Invalid blob') } })
+      } catch (error) {
+        this.onerror({ target: { error } })
+      }
+    }
+  },
+}