diff --git a/testing/errors/subst1.a b/testing/errors/subst1.a
new file mode 100644
index 0000000..fae1e0e
--- /dev/null
+++ b/testing/errors/subst1.a
@@ -0,0 +1,3 @@
+	*=$1000
+	;sub= we do not define sub at all
+base?sub	nop	; -> "neither number nor string"
diff --git a/testing/errors/subst2.a b/testing/errors/subst2.a
new file mode 100644
index 0000000..013f6da
--- /dev/null
+++ b/testing/errors/subst2.a
@@ -0,0 +1,3 @@
+	*=$1000
+	!set sub = [2,3]	; sub is a list
+base?sub	nop	; -> "neither number nor string"
diff --git a/testing/errors/subst3.a b/testing/errors/subst3.a
new file mode 100644
index 0000000..ed720ba
--- /dev/null
+++ b/testing/errors/subst3.a
@@ -0,0 +1,3 @@
+	*=$1000
+		lda sub	; sub is undefined
+base?sub	nop	; -> "undefined or not integer"
diff --git a/testing/errors/subst4.a b/testing/errors/subst4.a
new file mode 100644
index 0000000..af49592
--- /dev/null
+++ b/testing/errors/subst4.a
@@ -0,0 +1,3 @@
+	*=$1000
+	!set sub = .5	; sub is a float
+base?sub	nop	; -> "undefined or not integer"
diff --git a/testing/errors/subst5.a b/testing/errors/subst5.a
new file mode 100644
index 0000000..2985314
--- /dev/null
+++ b/testing/errors/subst5.a
@@ -0,0 +1,3 @@
+	*=$1000
+	!set sub = 7	; sub is defined okay, but:
+base?(sub	nop	; -> "does not end with ')' character."