diff --git a/jerry-core/ecma/builtin-objects/ecma-builtins.c b/jerry-core/ecma/builtin-objects/ecma-builtins.c
index 2eef37ccc..44b2074cf 100644
--- a/jerry-core/ecma/builtin-objects/ecma-builtins.c
+++ b/jerry-core/ecma/builtin-objects/ecma-builtins.c
@@ -253,7 +253,7 @@ ecma_instantiate_builtin (ecma_builtin_id_t id) /**< built-in id */
     {
       JERRY_ASSERT (id < ECMA_BUILTIN_ID__COUNT);
 
-      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+      JERRY_UNREACHABLE (); /* The built-in is not implemented. */
     }
   }
 } /* ecma_instantiate_builtin */
@@ -683,7 +683,7 @@ ecma_builtin_dispatch_routine (ecma_builtin_id_t builtin_object_id, /**< built-i
 
     default:
     {
-      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+      JERRY_UNREACHABLE (); /* The built-in is not implemented. */
     }
   }
 
@@ -744,7 +744,7 @@ ecma_builtin_dispatch_call (ecma_object_t *obj_p, /**< built-in object */
 
       default:
       {
-        JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+        JERRY_UNREACHABLE (); /* The built-in is not implemented. */
       }
     }
   }
@@ -799,7 +799,7 @@ ecma_builtin_dispatch_construct (ecma_object_t *obj_p, /**< built-in object */
 
     default:
     {
-      JERRY_UNIMPLEMENTED ("The built-in is not implemented.");
+      JERRY_UNREACHABLE (); /* The built-in is not implemented. */
     }
   }
 
diff --git a/jerry-core/jerry-port.h b/jerry-core/jerry-port.h
index d5d1faa4e..19f956d6a 100644
--- a/jerry-core/jerry-port.h
+++ b/jerry-core/jerry-port.h
@@ -48,7 +48,6 @@ typedef enum
   ERR_OUT_OF_MEMORY = 10,
   ERR_SYSCALL = 11,
   ERR_REF_COUNT_LIMIT = 12,
-  ERR_UNIMPLEMENTED_CASE = 118,
   ERR_FAILED_INTERNAL_ASSERTION = 120
 } jerry_fatal_code_t;
 
diff --git a/jerry-core/jerry.c b/jerry-core/jerry.c
index 3abcffd66..525fcc7c6 100644
--- a/jerry-core/jerry.c
+++ b/jerry-core/jerry.c
@@ -1821,7 +1821,7 @@ snapshot_add_compiled_code (ecma_compiled_code_t *compiled_code_p, /**< compiled
     copied_code_p->status_flags = compiled_code_p->status_flags;
 
 #else /* CONFIG_DISABLE_REGEXP_BUILTIN */
-    JERRY_UNIMPLEMENTED ("RegExp is not supported in the selected profile.");
+    JERRY_UNREACHABLE (); /* RegExp is not supported in the selected profile. */
 #endif /* !CONFIG_DISABLE_REGEXP_BUILTIN */
     return start_offset;
   }
@@ -2117,7 +2117,7 @@ snapshot_load_compiled_code (const uint8_t *snapshot_data_p, /**< snapshot data
 
     return (ecma_compiled_code_t *) re_bytecode_p;
 #else /* CONFIG_DISABLE_REGEXP_BUILTIN */
-    JERRY_UNIMPLEMENTED ("RegExp is not supported in the selected profile.");
+    JERRY_UNREACHABLE (); /* RegExp is not supported in the selected profile. */
 #endif /* !CONFIG_DISABLE_REGEXP_BUILTIN */
   }
 
diff --git a/jerry-core/jrt/jrt-fatals.c b/jerry-core/jrt/jrt-fatals.c
index 9c829d18d..8335408c2 100644
--- a/jerry-core/jrt/jrt-fatals.c
+++ b/jerry-core/jrt/jrt-fatals.c
@@ -51,11 +51,6 @@ jerry_fatal (jerry_fatal_code_t code) /**< status code */
       jerry_port_log (JERRY_LOG_LEVEL_ERROR, "Error: ERR_REF_COUNT_LIMIT\n");
       break;
     }
-    case ERR_UNIMPLEMENTED_CASE:
-    {
-      jerry_port_log (JERRY_LOG_LEVEL_ERROR, "Error: ERR_UNIMPLEMENTED_CASE\n");
-      break;
-    }
     case ERR_FAILED_INTERNAL_ASSERTION:
     {
       jerry_port_log (JERRY_LOG_LEVEL_ERROR, "Error: ERR_FAILED_INTERNAL_ASSERTION\n");
@@ -72,6 +67,7 @@ jerry_fatal (jerry_fatal_code_t code) /**< status code */
   }
 } /* jerry_fatal */
 
+#ifndef JERRY_NDEBUG
 /**
  * Handle failed assertion
  */
@@ -81,19 +77,12 @@ jerry_assert_fail (const char *assertion, /**< assertion condition string */
                    const char *function, /**< function name */
                    const uint32_t line) /**< line */
 {
-#ifndef JERRY_NDEBUG
   jerry_port_log (JERRY_LOG_LEVEL_ERROR,
                   "ICE: Assertion '%s' failed at %s(%s):%lu.\n",
                   assertion,
                   file,
                   function,
                   (unsigned long) line);
-#else /* JERRY_NDEBUG */
-  (void) assertion;
-  (void) file;
-  (void) function;
-  (void) line;
-#endif /* !JERRY_NDEBUG */
 
   jerry_fatal (ERR_FAILED_INTERNAL_ASSERTION);
 } /* jerry_assert_fail */
@@ -102,62 +91,16 @@ jerry_assert_fail (const char *assertion, /**< assertion condition string */
  * Handle execution of control path that should be unreachable
  */
 void __noreturn
-jerry_unreachable (const char *comment, /**< comment to unreachable mark if exists,
-                                             NULL - otherwise */
-                   const char *file, /**< file name */
+jerry_unreachable (const char *file, /**< file name */
                    const char *function, /**< function name */
                    const uint32_t line) /**< line */
 {
-#ifndef JERRY_NDEBUG
   jerry_port_log (JERRY_LOG_LEVEL_ERROR,
-                  "ICE: Unreachable control path at %s(%s):%lu was executed",
+                  "ICE: Unreachable control path at %s(%s):%lu was executed.\n",
                   file,
                   function,
                   (unsigned long) line);
-#else /* JERRY_NDEBUG */
-  (void) file;
-  (void) function;
-  (void) line;
-#endif /* !JERRY_NDEBUG */
-
-  if (comment != NULL)
-  {
-    jerry_port_log (JERRY_LOG_LEVEL_ERROR, "(%s)", comment);
-  }
-
-  jerry_port_log (JERRY_LOG_LEVEL_ERROR, ".\n");
 
   jerry_fatal (ERR_FAILED_INTERNAL_ASSERTION);
 } /* jerry_unreachable */
-
-/**
- * Handle unimplemented case execution
- */
-void __noreturn
-jerry_unimplemented (const char *comment, /**< comment to unimplemented mark if exists,
-                                               NULL - otherwise */
-                     const char *file, /**< file name */
-                     const char *function, /**< function name */
-                     const uint32_t line) /**< line */
-{
-#ifndef JERRY_NDEBUG
-  jerry_port_log (JERRY_LOG_LEVEL_ERROR,
-                  "SORRY: Unimplemented case at %s(%s):%lu was executed",
-                  file,
-                  function,
-                  (unsigned long) line);
-#else /* JERRY_NDEBUG */
-  (void) file;
-  (void) function;
-  (void) line;
 #endif /* !JERRY_NDEBUG */
-
-  if (comment != NULL)
-  {
-    jerry_port_log (JERRY_LOG_LEVEL_ERROR, "(%s)", comment);
-  }
-
-  jerry_port_log (JERRY_LOG_LEVEL_ERROR, ".\n");
-
-  jerry_fatal (ERR_UNIMPLEMENTED_CASE);
-} /* jerry_unimplemented */
diff --git a/jerry-core/jrt/jrt.h b/jerry-core/jrt/jrt.h
index 0ff09837f..2aa1883b9 100644
--- a/jerry-core/jrt/jrt.h
+++ b/jerry-core/jrt/jrt.h
@@ -24,7 +24,7 @@
 #include "jerry-port.h"
 #include "jrt-types.h"
 
-/**
+/*
  * Attributes
  */
 #define __noreturn __attribute__((noreturn))
@@ -40,7 +40,13 @@
 # define __attr_pure___ __attribute__((pure))
 #endif /* !__attr_pure___ */
 
-/**
+/*
+ * Conditions' likeliness, unlikeliness.
+ */
+#define likely(x) __builtin_expect (!!(x), 1)
+#define unlikely(x) __builtin_expect (!!(x) , 0)
+
+/*
  * Normally compilers store const(ant)s in ROM. Thus saving RAM.
  * But if your compiler does not support it then the directive below can force it.
  *
@@ -51,16 +57,17 @@
 # define JERRY_CONST_DATA
 #endif /* JERRY_CONST_DATA */
 
-#ifndef __GNUC__
-#define __extension__
-#endif /* !__GNUC__ */
-
-/**
+/*
  * Constants
  */
 #define JERRY_BITSINBYTE 8
 
-/**
+/*
+ * Make sure unused parameters, variables, or expressions trigger no compiler warning.
+ */
+#define JERRY_UNUSED(x) ((void) (x))
+
+/*
  * Asserts
  *
  * Warning:
@@ -73,30 +80,54 @@
 #define JERRY_STATIC_ASSERT(x, msg) \
   enum { JERRY_STATIC_ASSERT_GLUE (static_assertion_failed_, __LINE__, msg) = 1 / (!!(x)) }
 
-/**
- * Variable that must not be referenced.
- *
- * May be used for static assertion checks.
- */
-extern uint32_t jerry_unreferenced_expression;
-
-extern void __noreturn jerry_assert_fail (const char *, const char *, const char *, const uint32_t);
-extern void __noreturn jerry_unreachable (const char *, const char *, const char *, const uint32_t);
-extern void __noreturn jerry_unimplemented (const char *, const char *, const char *, const uint32_t);
-
 #ifndef JERRY_NDEBUG
-#define JERRY_ASSERT(x) do { if (__builtin_expect (!(x), 0)) { \
-    jerry_assert_fail (#x, __FILE__, __func__, __LINE__); } } while (0)
+extern void __noreturn jerry_assert_fail (const char *, const char *, const char *, const uint32_t);
+extern void __noreturn jerry_unreachable (const char *, const char *, const uint32_t);
+
+#define JERRY_ASSERT(x) \
+  do \
+  { \
+    if (unlikely (!(x))) \
+    { \
+      jerry_assert_fail (#x, __FILE__, __func__, __LINE__); \
+    } \
+  } while (0)
+
+#define JERRY_UNREACHABLE() \
+  do \
+  { \
+    jerry_unreachable (__FILE__, __func__, __LINE__); \
+  } while (0)
 #else /* JERRY_NDEBUG */
-#define JERRY_ASSERT(x) do { if (false) { (void)(x); } } while (0)
+#define JERRY_ASSERT(x) \
+  do \
+  { \
+    if (false) \
+    { \
+      JERRY_UNUSED (x); \
+    } \
+  } while (0)
+
+#define JERRY_UNREACHABLE() __builtin_unreachable ()
 #endif /* !JERRY_NDEBUG */
 
-#define JERRY_UNUSED(x) ((void) (x))
+/**
+ * Exit on fatal error
+ */
+extern void __noreturn jerry_fatal (jerry_fatal_code_t);
 
+/*
+ * Logging
+ */
 #ifdef JERRY_ENABLE_LOG
 #define JERRY_DLOG(...) jerry_port_log (JERRY_LOG_LEVEL_DEBUG, __VA_ARGS__)
 #define JERRY_DDLOG(...) jerry_port_log (JERRY_LOG_LEVEL_TRACE, __VA_ARGS__)
 #else /* !JERRY_ENABLE_LOG */
+/**
+ * Mark for unreachable points and unimplemented cases
+ */
+extern void jerry_ref_unused_variables (void *, ...);
+
 #define JERRY_DLOG(...) \
   do \
   { \
@@ -112,76 +143,10 @@ extern void __noreturn jerry_unimplemented (const char *, const char *, const ch
 #define JERRY_WARNING_MSG(...) jerry_port_log (JERRY_LOG_LEVEL_WARNING, __VA_ARGS__)
 
 /**
- * Mark for unreachable points and unimplemented cases
- */
-extern void jerry_ref_unused_variables (void *, ...);
-
-#ifndef JERRY_NDEBUG
-#define JERRY_UNREACHABLE() \
-  do \
-  { \
-    jerry_unreachable (NULL, __FILE__, __func__, __LINE__); \
-  } while (0)
-
-#define JERRY_UNIMPLEMENTED(comment) \
-  do \
-  { \
-    jerry_unimplemented (comment, __FILE__, __func__, __LINE__); \
-  } while (0)
-
-#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(comment, ...) \
-  do \
-  { \
-    if (false) \
-    { \
-      jerry_ref_unused_variables (0, __VA_ARGS__); \
-    } \
-    jerry_unimplemented (comment, __FILE__, __func__, __LINE__); \
-  } while (0)
-#else /* JERRY_NDEBUG */
-#define JERRY_UNREACHABLE() \
-  do \
-  { \
-    jerry_unreachable (NULL, NULL, NULL, 0); \
-  } while (0)
-
-#define JERRY_UNIMPLEMENTED(comment) \
-  do \
-  { \
-    jerry_unimplemented (comment, NULL, NULL, 0); \
-  } while (0)
-
-#define JERRY_UNIMPLEMENTED_REF_UNUSED_VARS(comment, ...) \
-  do \
-  { \
-    if (false) \
-    { \
-      jerry_ref_unused_variables (0, __VA_ARGS__); \
-    } \
-    jerry_unimplemented (comment, NULL, NULL, 0); \
-  } while (0)
-#endif /* !JERRY_NDEBUG */
-
-/**
- * Conditions' likeliness, unlikeliness.
- */
-#define likely(x) __builtin_expect (!!(x), 1)
-#define unlikely(x) __builtin_expect (!!(x) , 0)
-
-/**
- * Exit
- */
-extern void __noreturn jerry_fatal (jerry_fatal_code_t);
-
-/**
- * sizeof, offsetof, ...
+ * Size of struct member
  */
 #define JERRY_SIZE_OF_STRUCT_MEMBER(struct_name, member_name) sizeof (((struct_name *) NULL)->member_name)
 
-/**
- * Alignment
- */
-
 /**
  * Aligns @a value to @a alignment. @a must be the power of 2.
  *
@@ -189,15 +154,13 @@ extern void __noreturn jerry_fatal (jerry_fatal_code_t);
  */
 #define JERRY_ALIGNUP(value, alignment) (((value) + ((alignment) - 1)) & ~((alignment) - 1))
 
-/**
+/*
  * min, max
  */
 #define JERRY_MIN(v1, v2) (((v1) < (v2)) ? (v1) : (v2))
 #define JERRY_MAX(v1, v2) (((v1) < (v2)) ? (v2) : (v1))
 
-
 extern bool jrt_read_from_buffer_by_offset (const uint8_t *, size_t, size_t *, void *, size_t);
-
 extern bool jrt_write_to_buffer_by_offset (uint8_t *, size_t, size_t *, const void *, size_t);
 
 #endif /* !JRT_H */
diff --git a/jerry-core/vm/vm.c b/jerry-core/vm/vm.c
index 82c493aaa..7b9ae6629 100644
--- a/jerry-core/vm/vm.c
+++ b/jerry-core/vm/vm.c
@@ -301,7 +301,7 @@ vm_construct_literal_object (vm_frame_ctx_t *frame_ctx_p, /**< frame context */
 
     return ret_value;
 #else /* CONFIG_DISABLE_REGEXP_BUILTIN */
-    JERRY_UNIMPLEMENTED ("Regular Expressions are not supported in the selected profile!");
+    JERRY_UNREACHABLE (); /* Regular Expressions are not supported in the selected profile! */
 #endif /* !CONFIG_DISABLE_REGEXP_BUILTIN */
   }
 } /* vm_construct_literal_object */
diff --git a/tests/unit/test-common.h b/tests/unit/test-common.h
index eb210d6b6..cc7fc4a96 100644
--- a/tests/unit/test-common.h
+++ b/tests/unit/test-common.h
@@ -1,4 +1,5 @@
 /* Copyright 2014-2016 Samsung Electronics Co., Ltd.
+ * Copyright 2016 University of Szeged
  *
  * Licensed under the Apache License, Version 2.0 (the "License");
  * you may not use this file except in compliance with the License.
@@ -25,8 +26,20 @@
 #include <stdarg.h>
 #include <string.h>
 
-#define TEST_ASSERT(x) do { if (__builtin_expect (!(x), 0)) { \
-    jerry_assert_fail (#x, __FILE__, __func__, __LINE__); } } while (0)
+#define TEST_ASSERT(x) \
+  do \
+  { \
+    if (unlikely (!(x))) \
+    { \
+      jerry_port_log (JERRY_LOG_LEVEL_ERROR, \
+                      "TEST: Assertion '%s' failed at %s(%s):%lu.\n", \
+                      #x, \
+                      __FILE__, \
+                      __func__, \
+                      (unsigned long) __LINE__); \
+      jerry_fatal (ERR_FAILED_INTERNAL_ASSERTION); \
+    } \
+  } while (0)
 
 /**
  * Test initialization statement that should be included