Add ChecksumCalculator tests

Author: LeanBitLab

app/src/test/java/helium314/keyboard/latin/utils/ChecksumCalculatorTest.kt

@@ -0,0 +1,58 @@
+package helium314.keyboard.latin.utils
+
+import org.junit.Assert.assertEquals
+import org.junit.Test
+import java.io.ByteArrayInputStream
+import java.io.File
+import java.nio.file.Files
+
+class ChecksumCalculatorTest {
+
+    @Test
+    fun checksum_emptyInputStream_returnsExpectedHash() {
+        val emptyStream = ByteArrayInputStream(ByteArray(0))
+        val result = ChecksumCalculator.checksum(emptyStream)
+        // SHA-256 for empty string
+        assertEquals("e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855", result)
+    }
+
+    @Test
+    fun checksum_stringInputStream_returnsExpectedHash() {
+        val stream = ByteArrayInputStream("hello world".toByteArray())
+        val result = ChecksumCalculator.checksum(stream)
+        // SHA-256 for "hello world"
+        assertEquals("b94d27b9934d3e08a52e52d7da7dabfac484efe37a5380ee9088f7ace2efcde9", result)
+    }
+
+    @Test
+    fun checksum_largeInputStream_returnsExpectedHash() {
+        // Create an input larger than 8192 buffer to exercise the while loop
+        val largeData = ByteArray(10000) { it.toByte() }
+        val stream = ByteArrayInputStream(largeData)
+        val result = ChecksumCalculator.checksum(stream)
+
+        // Let's compute the hash separately or use a known one. We can use MessageDigest directly here to verify
+        val digester = java.security.MessageDigest.getInstance("SHA-256")
+        val expectedDigest = digester.digest(largeData)
+        val s = java.lang.StringBuilder()
+        for (i in expectedDigest.indices) {
+            s.append(String.format("%1$02x", expectedDigest[i]))
+        }
+        val expected = s.toString()
+
+        assertEquals(expected, result)
+    }
+
+    @Test
+    fun checksum_file_returnsExpectedHash() {
+        val tempFile = Files.createTempFile("test", ".txt").toFile()
+        try {
+            tempFile.writeText("file content")
+            val result = ChecksumCalculator.checksum(tempFile)
+            // SHA-256 for "file content"
+            assertEquals("e0ac3601005dfa1864f5392aabaf7d898b1b5bab854f1acb4491bcd806b76b0c", result)
+        } finally {
+            tempFile.delete()
+        }
+    }
+}