diff --git a/include/gfx/main.hpp b/include/gfx/main.hpp
index 52001389..bcaf69a5 100644
--- a/include/gfx/main.hpp
+++ b/include/gfx/main.hpp
@@ -41,7 +41,6 @@ struct Options {
 		uint16_t height;
 		uint32_t right() const { return left + width * 8; }
 		uint32_t bottom() const { return top + height * 8; }
-		bool specified() const { return left || top || width || height; }
 	} inputSlice{0, 0, 0, 0};                          // -L (margins in clockwise order, like CSS)
 	uint8_t basePalID = 0;                             // -l
 	std::array<uint16_t, 2> maxNbTiles{UINT16_MAX, 0}; // -N
diff --git a/src/gfx/main.cpp b/src/gfx/main.cpp
index 24959c0d..d550c39d 100644
--- a/src/gfx/main.cpp
+++ b/src/gfx/main.cpp
@@ -632,7 +632,8 @@ static void verboseOutputConfig() {
 		fputs("\t]\n", stderr);
 	}
 	// -L/--slice
-	if (options.inputSlice.specified()) {
+	if (options.inputSlice.width || options.inputSlice.height || options.inputSlice.left
+	    || options.inputSlice.top) {
 		fprintf(
 		    stderr,
 		    "\tInput image slice: %" PRIu16 "x%" PRIu16 " pixels starting at (%" PRIu16 ", %" PRIu16
diff --git a/src/util.cpp b/src/util.cpp
index c530d135..24bf6f5a 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -84,6 +84,8 @@ std::optional<uint64_t> parseNumber(char const *&str, NumberBase base) {
 	// Identify the base if not specified
 	// Does *not* support '+' or '-' sign prefix (unlike `strtoul` and `std::from_chars`)
 	if (base == BASE_AUTO) {
+		base = BASE_10;
+
 		// Skips leading blank space (like `strtoul`)
 		str += strspn(str, " \t");
 
@@ -118,17 +120,10 @@ std::optional<uint64_t> parseNumber(char const *&str, NumberBase base) {
 				base = BASE_16;
 				str += 2;
 				break;
-			default:
-				base = BASE_10;
-				break;
 			}
 			break;
-		default:
-			base = BASE_10;
-			break;
 		}
 	}
-	assume(base != BASE_AUTO);
 
 	// Get the digit-condition function corresponding to the base
 	bool (*canParseDigit)(int c) = base == BASE_2    ? isBinDigit
diff --git a/test/asm/backtrace-collapsed.asm b/test/asm/backtrace-collapsed.asm
new file mode 100644
index 00000000..a9a39643
--- /dev/null
+++ b/test/asm/backtrace-collapsed.asm
@@ -0,0 +1,15 @@
+macro careful
+	if _NARG == 20
+		warn "You're in too deep!"
+	else
+		careful \#, deeper
+	endc
+endm
+careful surface
+
+macro recurse
+	recurse
+endm
+rept 3
+	recurse
+endr
diff --git a/test/asm/backtrace-collapsed.err b/test/asm/backtrace-collapsed.err
new file mode 100644
index 00000000..5cf05544
--- /dev/null
+++ b/test/asm/backtrace-collapsed.err
@@ -0,0 +1,4 @@
+warning: You're in too deep! [-Wuser]
+    at backtrace-collapsed.asm::careful(3) <- backtrace-collapsed.asm::careful(5) <- backtrace-collapsed.asm::careful(5) <- ...16 more... <- backtrace-collapsed.asm::careful(5) <- backtrace-collapsed.asm(8)
+FATAL: Recursion limit (64) exceeded
+    at backtrace-collapsed.asm::recurse(11) <- backtrace-collapsed.asm::recurse(11) <- backtrace-collapsed.asm::recurse(11) <- ...60 more... <- backtrace-collapsed.asm::REPT~1(14) <- backtrace-collapsed.asm(13)
diff --git a/test/asm/backtrace-collapsed.flags b/test/asm/backtrace-collapsed.flags
new file mode 100644
index 00000000..4becafe6
--- /dev/null
+++ b/test/asm/backtrace-collapsed.flags
@@ -0,0 +1 @@
+-B 5 -B collapse
diff --git a/test/asm/cli/empty-s-feature.err b/test/asm/cli/empty-s-feature.err
new file mode 100644
index 00000000..bd1d26b3
--- /dev/null
+++ b/test/asm/cli/empty-s-feature.err
@@ -0,0 +1 @@
+FATAL: Empty feature for option '-s'
diff --git a/test/asm/cli/empty-s-feature.flags b/test/asm/cli/empty-s-feature.flags
new file mode 100644
index 00000000..a05de48f
--- /dev/null
+++ b/test/asm/cli/empty-s-feature.flags
@@ -0,0 +1 @@
+-s :-
diff --git a/test/asm/cli/invalid-color.flags b/test/asm/cli/invalid-color.flags
index 155f9e88..e9becb2a 100644
--- a/test/asm/cli/invalid-color.flags
+++ b/test/asm/cli/invalid-color.flags
@@ -1 +1 @@
---color yes
+--color=always --color=never --color=auto --color=yes
diff --git a/test/asm/cli/invalid-s-feature.err b/test/asm/cli/invalid-s-feature.err
new file mode 100644
index 00000000..16f6ba9a
--- /dev/null
+++ b/test/asm/cli/invalid-s-feature.err
@@ -0,0 +1 @@
+FATAL: Invalid feature for option '-s': "invalid"
diff --git a/test/asm/cli/invalid-s-feature.flags b/test/asm/cli/invalid-s-feature.flags
new file mode 100644
index 00000000..e1fa0082
--- /dev/null
+++ b/test/asm/cli/invalid-s-feature.flags
@@ -0,0 +1 @@
+-s invalid:-
diff --git a/test/asm/disable-warnings.asm b/test/asm/disable-warnings.asm
new file mode 100644
index 00000000..4e050ffc
--- /dev/null
+++ b/test/asm/disable-warnings.asm
@@ -0,0 +1,10 @@
+MACRO test
+	assert warn, 0, "-Wassert is on by default"
+	warn "-Wuser is on by default"
+ENDM
+
+test ; no warnings because of -w
+OPT -Weverything
+test ; still no warnings because of -w
+OPT Werror=everything
+test ; now errors can occur
diff --git a/test/asm/disable-warnings.flags b/test/asm/disable-warnings.flags
new file mode 100644
index 00000000..e1350473
--- /dev/null
+++ b/test/asm/disable-warnings.flags
@@ -0,0 +1 @@
+-w
diff --git a/test/asm/loud-backtrace.flags b/test/asm/loud-backtrace.flags
index fbe5fd01..9e9e9ddc 100644
--- a/test/asm/loud-backtrace.flags
+++ b/test/asm/loud-backtrace.flags
@@ -1 +1 @@
--B all
+-B no-all -B all
diff --git a/test/asm/make-deps.asm b/test/asm/make-deps.asm
new file mode 100644
index 00000000..e69de29b
diff --git a/test/asm/make-deps.flags b/test/asm/make-deps.flags
new file mode 100644
index 00000000..79d5c00e
--- /dev/null
+++ b/test/asm/make-deps.flags
@@ -0,0 +1 @@
+-M - -MT preserve$dollars$$ -MQ escape$dollars$$
diff --git a/test/asm/make-deps.out b/test/asm/make-deps.out
new file mode 100644
index 00000000..201f4867
--- /dev/null
+++ b/test/asm/make-deps.out
@@ -0,0 +1 @@
+preserve$dollars$$ escape$$dollars$$$$: make-deps.asm
diff --git a/test/asm/opt-r.flags b/test/asm/opt-r.flags
new file mode 100644
index 00000000..843dac5e
--- /dev/null
+++ b/test/asm/opt-r.flags
@@ -0,0 +1 @@
+-r9 -r$f -r%1 -r&7 -r0xFF -r0b11 -r0o77 -r64
diff --git a/test/asm/state-features.asm b/test/asm/state-features.asm
new file mode 100644
index 00000000..c3c2b268
--- /dev/null
+++ b/test/asm/state-features.asm
@@ -0,0 +1,7 @@
+MACRO one
+!@#$%^&* /* anything */ :'<,>./? ; goes!
+ENDM
+CHARMAP "char", 2, 3
+DEF string EQUS "four"
+DEF variable = 5
+DEF constant EQU 6
diff --git a/test/asm/state-features.err b/test/asm/state-features.err
new file mode 100644
index 00000000..b6193cc9
--- /dev/null
+++ b/test/asm/state-features.err
@@ -0,0 +1,2 @@
+warning: Ignoring duplicate feature for option '-s': "equ"
+warning: Redundant feature before "all" for option '-s'
diff --git a/test/asm/state-features.flags b/test/asm/state-features.flags
new file mode 100644
index 00000000..c1c49bd3
--- /dev/null
+++ b/test/asm/state-features.flags
@@ -0,0 +1 @@
+-s equ,var,equ,all:-
diff --git a/test/asm/state-features.out b/test/asm/state-features.out
new file mode 100644
index 00000000..4e9ae314
--- /dev/null
+++ b/test/asm/state-features.out
@@ -0,0 +1,19 @@
+; File generated by rgbasm
+
+; Numeric constants
+def constant equ $6
+
+; Variables
+def variable = $5
+
+; String constants
+def string equs "four"
+
+; Character maps
+newcharmap main
+charmap "char", $2, $3
+
+; Macros
+macro one
+!@#$%^&* /* anything */ :'<,>./? ; goes!
+endm
diff --git a/test/asm/test.sh b/test/asm/test.sh
index 6d51a36a..5c879603 100755
--- a/test/asm/test.sh
+++ b/test/asm/test.sh
@@ -84,10 +84,11 @@ for i in *.asm notexist.asm; do
 			desired_output=$desired_outname
 			desired_errput=$desired_errname
 		else
-			# `include-recursion.asm` refers to its own name inside the test code.
-			# "notexist" doesn't exist, so there's no point in trying to `cat` it.
-			# Skip testing with stdin input for those file.
-			if [[ "$i" = include-recursion.asm || "$i" = notexist.asm ]]; then
+			# "include-recursion.asm" refers to its own name inside the test code.
+			# "make-deps.asm" refers to its output filename in its desired output.
+			# "notexist.asm" doesn't exist, so there's no point in trying to `cat` it.
+			# Skip testing with stdin input for those files.
+			if [[ "$i" = include-recursion.asm || "$i" = make-deps.asm || "$i" = notexist.asm ]]; then
 				continue
 			fi
 
@@ -193,18 +194,20 @@ i="state-file"
 if which cygpath &>/dev/null; then
 	# MinGW translates path names before passing them as command-line arguments,
 	# but does not do so when they are prefixed, so we have to do it ourselves.
-	RGBASMFLAGS="-Weverything -Bcollapse -s all:$(cygpath -w "$o")"
+	state_outname="$(cygpath -w "$o")"
 else
-	RGBASMFLAGS="-Weverything -Bcollapse -s all:$o"
+	state_outname="$o"
 fi
+state_features="  all  " # Test trimming whitespace
+RGBASMFLAGS="-Weverything -Bcollapse"
 for variant in '' '.pipe'; do
 	(( tests++ ))
 	echo "${bold}${green}${i%.asm}${variant}...${rescolors}${resbold}"
 	if [ -z "$variant" ]; then
-		"$RGBASM" $RGBASMFLAGS "$i"/a.asm >"$output" 2>"$errput"
+		"$RGBASM" $RGBASMFLAGS -s "$state_features:$state_outname" "$i"/a.asm >"$output" 2>"$errput"
 	else
 		# shellcheck disable=SC2002
-		cat "$i"/a.asm | "$RGBASM" $RGBASMFLAGS - >"$output" 2>"$errput"
+		cat "$i"/a.asm | "$RGBASM" $RGBASMFLAGS -s "$state_features:$state_outname" - >"$output" 2>"$errput"
 	fi
 
 	tryDiff /dev/null "$output" out
diff --git a/test/asm/unknown-warning.asm b/test/asm/unknown-warning.asm
new file mode 100644
index 00000000..e69de29b
diff --git a/test/asm/unknown-warning.err b/test/asm/unknown-warning.err
new file mode 100644
index 00000000..3d88681e
--- /dev/null
+++ b/test/asm/unknown-warning.err
@@ -0,0 +1,2 @@
+warning: Unknown warning flag "noexist"
+warning: Unknown warning flag parameter "noexistparam=2"
diff --git a/test/asm/unknown-warning.flags b/test/asm/unknown-warning.flags
new file mode 100644
index 00000000..55c3eaac
--- /dev/null
+++ b/test/asm/unknown-warning.flags
@@ -0,0 +1 @@
+-Wnoexist -Wnoexistparam=2
diff --git a/test/asm/warning-as-error.asm b/test/asm/warning-as-error.asm
new file mode 100644
index 00000000..7d2c1231
--- /dev/null
+++ b/test/asm/warning-as-error.asm
@@ -0,0 +1,14 @@
+DEF n = -99 >> 1 ; -Wshift
+DEF n = 999_999_999_999 ; -Wlarge-constant
+
+MACRO test
+	WARN "warning or error?"
+ENDM
+
+test
+
+OPT Werror
+test
+
+OPT Wno-error
+test
diff --git a/test/asm/warning-as-error.err b/test/asm/warning-as-error.err
new file mode 100644
index 00000000..2c0f5433
--- /dev/null
+++ b/test/asm/warning-as-error.err
@@ -0,0 +1,10 @@
+warning: Shifting right negative value -99 [-Wshift]
+    at warning-as-error.asm(1)
+error: Integer constant is too large [-Werror=large-constant]
+    at warning-as-error.asm(2)
+warning: warning or error? [-Wuser]
+    at warning-as-error.asm::test(5) <- warning-as-error.asm(8)
+error: warning or error? [-Werror=user]
+    at warning-as-error.asm::test(5) <- warning-as-error.asm(11)
+warning: warning or error? [-Wuser]
+    at warning-as-error.asm::test(5) <- warning-as-error.asm(14)
diff --git a/test/asm/warning-as-error.flags b/test/asm/warning-as-error.flags
new file mode 100644
index 00000000..9c1bb799
--- /dev/null
+++ b/test/asm/warning-as-error.flags
@@ -0,0 +1 @@
+-Werror=shift -Wno-error=shift -Werror=large-constant