diff --git a/src/test/java/mpo/dayon/common/RunnerTest.java b/src/test/java/mpo/dayon/common/RunnerTest.java
index 2735e4a7..6a386f5f 100644
--- a/src/test/java/mpo/dayon/common/RunnerTest.java
+++ b/src/test/java/mpo/dayon/common/RunnerTest.java
@@ -69,8 +69,8 @@ void shouldExtractProgramArgs() {
         Map<String, String> programArgs = extractProgramArgs(args);
         // then
         assertEquals(2, programArgs.size(), "Unexpected number of extracted ProgramArgs");
-        assertEquals("en", programArgs.get("lang"), "Key 'lang' shold have value 'en'");
-        assertEquals("BAR", programArgs.get("foo"), "Key 'foo' shold have value 'BAR'");
+        assertEquals("en", programArgs.get("lang"), "Key 'lang' should have value 'en'");
+        assertEquals("BAR", programArgs.get("foo"), "Key 'foo' should have value 'BAR'");
     }
 
     @Test
diff --git a/src/test/java/mpo/dayon/common/buffer/MemByteBufferTest.java b/src/test/java/mpo/dayon/common/buffer/MemByteBufferTest.java
index af9655b6..04546b76 100644
--- a/src/test/java/mpo/dayon/common/buffer/MemByteBufferTest.java
+++ b/src/test/java/mpo/dayon/common/buffer/MemByteBufferTest.java
@@ -23,6 +23,14 @@ void tearDown() throws IOException {
         buffer.close();
     }
 
+    @Test
+    void write() {
+        final int val = 234;
+        buffer.write(val);
+        assertEquals(1, buffer.size());
+        assertEquals((byte) val, buffer.getInternal()[0]);
+    }
+
     @Test
     void writeInt() {
         buffer.writeInt(BEAST);
diff --git a/src/test/java/mpo/dayon/common/utils/SystemUtilitiesTest.java b/src/test/java/mpo/dayon/common/utils/SystemUtilitiesTest.java
index cb1fcd19..b3be6210 100644
--- a/src/test/java/mpo/dayon/common/utils/SystemUtilitiesTest.java
+++ b/src/test/java/mpo/dayon/common/utils/SystemUtilitiesTest.java
@@ -1,5 +1,6 @@
 package mpo.dayon.common.utils;
 
+import static java.lang.String.format;
 import static mpo.dayon.common.utils.SystemUtilities.*;
 import static org.junit.jupiter.api.Assertions.*;
 
@@ -7,6 +8,10 @@
 import org.junit.jupiter.params.ParameterizedTest;
 import org.junit.jupiter.params.provider.CsvSource;
 
+import java.io.File;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.security.NoSuchAlgorithmException;
 
 class SystemUtilitiesTest {
@@ -105,4 +110,17 @@ void isValidPortNumberShouldReturnTrueForValidPorts(String port) {
 		// when, then
 		assertTrue(isValidPortNumber(port));
 	}
+
+	@Test
+	void shouldObtainWritableTempDir() throws IOException {
+		// when, then
+		assertTrue(Files.isWritable(new File(getTempDir()).toPath()), "TempDir should be writable");
+	}
+
+	@Test
+	void shouldObtainJarDir() throws IOException {
+		// when, then
+		assertTrue(new File(format("%s%sdayon.jar", getJarDir(), File.separator)).exists(), "JarDir should contain dayon.jar");
+	}
+
 }