diff --git a/mocks/common/debug.cpp b/mocks/common/debug.cpp
new file mode 100644
index 0000000..4a9d7f2
--- /dev/null
+++ b/mocks/common/debug.cpp
@@ -0,0 +1,75 @@
+/*
+ * Copyright (c) 2017-2020, Arm Limited and Contributors. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdarg.h>
+#include <assert.h>
+#include <stdio.h>
+#include <setjmp.h>
+extern "C" {
+#include <common/debug.h>
+}
+
+#include "CppUTestExt/MockSupport.h"
+#include "common/mock_debug.h"
+
+/* Set the default maximum log level to the `LOG_LEVEL` build flag */
+static unsigned int max_log_level = LOG_LEVEL_VERBOSE;
+
+int expect_panic(panic_environment_t *env) {
+	mock("debug").expectOneCall("do_panic").andReturnValue(env);
+	return 1;
+}
+
+void expect_tf_log(const char *str) {
+	mock().expectOneCall("tf_log").withStringParameter("str", str);
+}
+
+extern "C" {
+void do_panic(void) {
+	panic_environment_t *env = (panic_environment_t *)mock("debug").actualCall("do_panic").returnPointerValue();
+	longjmp(*env, 1);
+}
+
+void tf_log(const char *fmt, ...)
+{
+	unsigned int log_level;
+	va_list args;
+	const char *prefix_str;
+
+	/* We expect the LOG_MARKER_* macro as the first character */
+	log_level = fmt[0];
+
+	/* Verify that log_level is one of LOG_MARKER_* macro defined in debug.h */
+	assert((log_level > 0U) && (log_level <= LOG_LEVEL_VERBOSE));
+	assert((log_level % 10U) == 0U);
+
+	if (log_level > max_log_level)
+		return;
+
+	char log_buffer[1024];
+	va_start(args, fmt);
+	(void)vsnprintf(log_buffer, sizeof(log_buffer), fmt + 1, args);
+	va_end(args);
+
+	mock().actualCall("tf_log").withStringParameter("str", log_buffer);
+}
+
+/*
+ * The helper function to set the log level dynamically by platform. The
+ * maximum log level is determined by `LOG_LEVEL` build flag at compile time
+ * and this helper can set a lower (or equal) log level than the one at compile.
+ */
+void tf_log_set_max_level(unsigned int log_level)
+{
+	assert(log_level <= LOG_LEVEL_VERBOSE);
+	assert((log_level % 10U) == 0U);
+
+	/* Cap log_level to the compile time maximum. */
+	if (log_level <= (unsigned int)LOG_LEVEL_VERBOSE)
+		max_log_level = log_level;
+}
+} // extern "C"
+