diff --git a/src/tests.asm b/src/tests.asm
index 0f85127..3d84e6f 100644
--- a/src/tests.asm
+++ b/src/tests.asm
@@ -2,6 +2,8 @@
 
 ; core.asm
 extern	exit
+extern	islower
+extern	isupper
 ; console.asm
 extern	print
 extern	puts
@@ -26,21 +28,28 @@ section .rodata
 	TEST_strcpy		equ	1
 	TEST_strcat		equ	1
 	TEST_strclr		equ	1
+	TEST_islower		equ	1
+	TEST_isupper		equ	1
 
 	str1			db	"Hello, world!",EOS
 	str2			db	"Hello, World!",EOS
 	str3			db	"Hello world!",EOS
 	str4			db	"Howdy environment!",EOS
 	str5			db	"The quick brown fox jumps over the lazy dog",EOS
+	msgStrings		db	"PRINT str1-5:",NL,"str1: %s",NL,"str2: %s",NL,"str3: %s",NL,"str4: %s",NL,"str5: %s",NL,NL,EOS
 
 	; print()
-	msgPrint		db	"TEST print()",NL,EOS
+	msgPrint		db	NL,"TEST print()",NL,EOS
 
 	; puts()
-	msgPuts			db	"TEST puts()",EOS
+	msgPuts			db	NL,"TEST puts()",EOS
+
+	; [u]dec2str() / hex2str()
+	msgDec2str		db	NL,"TEST dec2str() / udec2str()",NL,TAB,"Use GDB ('x/s $rax' after function call)",NL,TAB,"No tests printed - see printf outputs :)",NL,EOS
+	msgHex2str		db	NL,"TEST hex2str()",NL,TAB,"Use GDB ('x/s $rax' after function call)",NL,TAB,"No tests printed - see printf outputs :)",NL,EOS
 
 	; printf()
-	msgPrintf		db	"TEST printf()",NL,EOS
+	msgPrintf		db	NL,"TEST printf()",NL,EOS
 	printf1			db	TAB,"printf(",DQUO,"He%ll%o there%%%%%!%!%\n",DQUO,"): ",NL,TAB,TAB,EOS
 	printf1Str		db	"He%ll%o there%%%%%!%!%",NL,EOS
 	printf2			db	TAB,"printf(",DQUO,"Are %s doing %s?\n",DQUO,", printf2Str1, printf2Str2): ",NL,TAB,TAB,EOS
@@ -64,27 +73,45 @@ section .rodata
 	printf5Str		db	"%x|%X , %x|%X",NL,EOS
 
 	; strlen()
-	strlenStr1		db	"Hello",EOS
-	strlenStr2		db	"Hello, world!",NL,EOS
+	msgStrlen		db	NL,"TEST strlen()",NL,EOS
+	strlen1			db	TAB,"strlen(str1): %d",NL,EOS
+	strlen2			db	TAB,"strlen(str3): %d",NL,EOS
+	strlen3			db	TAB,"strlen(str5): %d",NL,EOS
 
 	; strcpy()
-	msgStrcpy		db	"TEST strcpy()",NL,EOS
+	msgStrcpy		db	NL,"TEST strcpy()",NL,EOS
 	strcpy1			db	TAB,"strcpy(strBuff1, str1, 12): ",NL,TAB,TAB,EOS
 	strcpy2			db	TAB,"strcpy(strBuff1, str1, 13): ",NL,TAB,TAB,EOS
 	strcpy3			db	TAB,"strcpy(strBuff1, str1, 32): ",NL,TAB,TAB,EOS
 	strcpy4			db	TAB,"strcpy(strBuff1, str5, 32): ",NL,TAB,TAB,EOS
 
 	; strcat()
-	msgStrcat		db	"TEST strcat()",NL,EOS
+	msgStrcat		db	NL,"TEST strcat()",NL,EOS
 	strcat1			db	TAB,"strcat(strBuff2, str1, 32): ",NL,TAB,TAB,EOS
 	strcat2			db	TAB,"strcat(strBuff2, str5, 32): ",NL,TAB,TAB,EOS
 
 	;strclr()
-	msgStrclr		db	"TEST strclr()",NL,EOS
+	msgStrclr		db	NL,"TEST strclr()",NL,EOS
 	strclr1a		db	TAB,"strcat(strBuff1, str5, 32)",NL,TAB,"strclr(strBuff1, 32)",NL,TAB,"print(strBuff1): ",NL,TAB,TAB,EOS
 	strclr1b		db	TAB,"print(strBuff1[3]): ",NL,TAB,TAB,EOS
 	strclr2			db	TAB,"strcat(strBuff1, str5, 32)",NL,TAB,"strclr(strbuff1, 2)",NL,TAB,"print(strbuff1[3]): ",NL,TAB,TAB,EOS
 
+	;islower()
+	msgIslower		db	NL,"TEST islower()",NL,EOS
+	islower1		db	TAB,"islower(str1[0]): %d",NL,EOS
+	islower2		db	TAB,"islower(str1[1]): %d",NL,EOS
+	islower3		db	TAB,"islower('d'): %d",NL,EOS
+	islower4		db	TAB,"islower('D'): %d",NL,EOS
+	islower5		db	TAB,"islower('!'): %d",NL,EOS
+
+	;isupper()
+	msgIsupper		db	NL,"TEST isupper()",NL,EOS
+	isupper1		db	TAB,"isupper(str1[0]): %d",NL,EOS
+	isupper2		db	TAB,"isupper(str1[1]): %d",NL,EOS
+	isupper3		db	TAB,"isupper('d'): %d",NL,EOS
+	isupper4		db	TAB,"isupper('D'): %d",NL,EOS
+	isupper5		db	TAB,"isupper('!'): %d",NL,EOS
+
 section .data
 
 section .bss
@@ -98,6 +125,15 @@ _start:
 	mov	rbp, rsp
 	sub	rsp, SIZE_QWORD
 
+; PRINT STRINGS
+	lea	rdi, [rel msgStrings]
+	lea	rsi, [rel str1]
+	lea	rdx, [rel str2]
+	lea	rcx, [rel str3]
+	lea	r8, [rel str4]
+	lea	r9, [rel str5]
+	call	printf
+
 ;---
 ;--- print()
 ;---
@@ -118,13 +154,19 @@ _start:
 ;--- dec2str() / udec2str()
 ;---
 %if TEST_dec2str
-	; x/s $rax after calls to confirm proper output
+	lea	rdi, [rel msgDec2str]
+	call	print
+
+	; TEST 1
 	mov	rdi, -569384
 	call	dec2str
+	; TEST 2
 	mov	rdi, -569384
 	call	udec2str
+	; TEST 3
 	mov	rdi, 0xFFFFFFFFFFFFFFFF
 	call	dec2str
+	; TEST 4
 	mov	rdi, 0xFFFFFFFFFFFFFFFF
 	call	udec2str
 %endif
@@ -133,6 +175,9 @@ _start:
 ;--- hex2str()
 ;---
 %if TEST_hex2str
+	lea	rdi, [rel msgHex2str]
+	call	print
+
 	; TEST 1
 	xor	rdi, rdi
 	mov	rsi, 0
@@ -229,12 +274,29 @@ _start:
 ;--- strlen()
 ;---
 %if TEST_strlen
+	lea	rdi, [rel msgStrlen]
+	call	print
+
 	; TEST 1
-	lea	rdi, [rel strlenStr1]
+	lea	rdi, [rel str1]
 	call	strlen
+	lea	rdi, [rel strlen1]
+	mov	rsi, rax
+	call	printf
+
 	; TEST 2
-	lea	rdi, [rel strlenStr2]
+	lea	rdi, [rel str3]
 	call	strlen
+	lea	rdi, [rel strlen2]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 3
+	lea	rdi, [rel str5]
+	call	strlen
+	lea	rdi, [rel strlen3]
+	mov	rsi, rax
+	call	printf
 %endif
 
 ;---
@@ -351,6 +413,92 @@ _start:
 	call puts
 %endif
 
+;---
+;--- islower()
+;---
+%if TEST_islower
+	lea	rdi, [rel msgIslower]
+	call	print
+
+	; TEST 1
+	mov	dil, byte [str1]
+	call	islower
+	lea	rdi, [rel islower1]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 2
+	mov	dil, byte [str1 + 1]
+	call	islower
+	lea	rdi, [rel islower2]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 3
+	mov	dil, 'd'
+	call	islower
+	lea	rdi, [rel islower3]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 4
+	mov	dil, 'D'
+	call	islower
+	lea	rdi, [rel islower4]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 5
+	mov	dil, '!'
+	call	islower
+	lea	rdi, [rel islower5]
+	mov	rsi, rax
+	call	printf
+%endif
+
+;---
+;--- isupper()
+;---
+%if TEST_isupper
+	lea	rdi, [rel msgIsupper]
+	call	print
+
+	; TEST 1
+	mov	dil, byte [str1]
+	call	isupper
+	lea	rdi, [rel isupper1]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 2
+	mov	dil, byte [str1 + 1]
+	call	isupper
+	lea	rdi, [rel isupper2]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 3
+	mov	dil, 'd'
+	call	isupper
+	lea	rdi, [rel isupper3]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 4
+	mov	dil, 'D'
+	call	isupper
+	lea	rdi, [rel isupper4]
+	mov	rsi, rax
+	call	printf
+
+	; TEST 5
+	mov	dil, '!'
+	call	isupper
+	lea	rdi, [rel isupper5]
+	mov	rsi, rax
+	call	printf
+%endif
+
 ;---
 ;--- exit()
 ;---