diff --git a/testing/btest/Baseline/language.closure-binding-deprecated/out b/testing/btest/Baseline/language.closure-binding-deprecated/out
new file mode 100644
index 0000000000..066ca90cec
--- /dev/null
+++ b/testing/btest/Baseline/language.closure-binding-deprecated/out
@@ -0,0 +1,12 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+reference capture
+4, 10
+6, 8
+7, 7
+reference double capture
+4
+2, 10, 47
+4
+2, 8, 47
+3
+1, 7, 47
diff --git a/testing/btest/Baseline/language.closure-binding/out b/testing/btest/Baseline/language.closure-binding/out
index 891492d324..d5c7c22634 100644
--- a/testing/btest/Baseline/language.closure-binding/out
+++ b/testing/btest/Baseline/language.closure-binding/out
@@ -1,43 +1,42 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
-4, 10
-6, 8
-7, 7
+shallow copy
 4, 10
 5, 8
 6, 7
+deep copy
 4, 10
 5, 9
 6, 8
+mixed copy, case 1
 4, 10
 5, 8
 6, 7
+mixed copy, case 2
 4, 10
 5, 9
 6, 8
-4
-2, 10, 47
-4
-2, 8, 47
-3
-1, 7, 47
+double shallow copy
 4
 2, 10, 47
 5
 3, 8, 47
 6
 4, 7, 47
+double deep copy, case 1
 4
 2, 10, 47
 5
 3, 9, 47
 6
 4, 8, 47
+double deep copy, case 2
 4
 2, 10, 91
 5
 3, 9, 91
 6
 4, 9, 91
+double deep copy, case 3
 4
 2, 10, 91
 5
diff --git a/testing/btest/Baseline/language.closure-sending-deprecated/recv.recv.out b/testing/btest/Baseline/language.closure-sending-deprecated/recv.recv.out
new file mode 100644
index 0000000000..d48a41b96d
--- /dev/null
+++ b/testing/btest/Baseline/language.closure-sending-deprecated/recv.recv.out
@@ -0,0 +1,27 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+hello :-)
+peer added
+receiver got ping: function 2
+inside: 1 | outside: 12 | global: 100
+77
+receiver got ping: function 1
+begin: 100 | base_step: 2
+begin: 100 | base_step: 2 | step: 76
+178
+receiver got ping: function 2
+inside: 3 | outside: 12 | global: 100
+79
+receiver got ping: function 1
+begin: 100 | base_step: 4
+begin: 100 | base_step: 4 | step: 76
+180
+receiver got ping: function 2
+inside: 5 | outside: 12 | global: 100
+81
+receiver got ping: function 1
+begin: 100 | base_step: 6
+begin: 100 | base_step: 6 | step: 76
+182
+receiver got ping: function 2
+inside: 7 | outside: 12 | global: 100
+83
diff --git a/testing/btest/Baseline/language.closure-sending-deprecated/send.send.out b/testing/btest/Baseline/language.closure-sending-deprecated/send.send.out
new file mode 100644
index 0000000000..39d70d48d5
--- /dev/null
+++ b/testing/btest/Baseline/language.closure-sending-deprecated/send.send.out
@@ -0,0 +1,32 @@
+### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
+hello :)
+peer added
+begin: 100 | base_step: 50
+sender got pong: function 2
+inside: 1 | outside: 12 | global: 10
+77
+begin: 100 | base_step: 50
+sender got pong: function 1
+begin: 178 | base_step: 2
+begin: 178 | base_step: 2 | step: 76
+256
+begin: 100 | base_step: 50
+sender got pong: function 2
+inside: 3 | outside: 12 | global: 10
+79
+begin: 100 | base_step: 50
+sender got pong: function 1
+begin: 180 | base_step: 4
+begin: 180 | base_step: 4 | step: 76
+260
+begin: 100 | base_step: 50
+sender got pong: function 2
+inside: 5 | outside: 12 | global: 10
+81
+begin: 100 | base_step: 50
+sender got pong: function 1
+begin: 182 | base_step: 6
+begin: 182 | base_step: 6 | step: 76
+264
+begin: 100 | base_step: 50
+peer lost
diff --git a/testing/btest/Baseline/language.uninitialized-local3/out b/testing/btest/Baseline/language.uninitialized-local3/out
index 70650b5bb5..e65bf87f36 100644
--- a/testing/btest/Baseline/language.uninitialized-local3/out
+++ b/testing/btest/Baseline/language.uninitialized-local3/out
@@ -1,6 +1,6 @@
 ### BTest baseline data generated by btest-diff. Do not edit. Use "btest -U/-u" to update. Requires BTest >= 0.63.
-warning in <...>/uninitialized-local3.zeek, line 33: possibly used without definition (x4)
-expression error in <...>/uninitialized-local3.zeek, line 33: value used but not set (x4)
+warning in <...>/uninitialized-local3.zeek, line 38: possibly used without definition (x4)
+expression error in <...>/uninitialized-local3.zeek, line 38: value used but not set (x4)
 x$a (x <...>/uninitialized-local3.zeek, line 20) possibly used without being set
 x$e (x <...>/uninitialized-local3.zeek, line 20) possibly used without being set
 x$e (x <...>/uninitialized-local3.zeek, line 24) possibly used without being set
diff --git a/testing/btest/core/conn-uid.zeek b/testing/btest/core/conn-uid.zeek
index 5852236ff0..6c7c326492 100644
--- a/testing/btest/core/conn-uid.zeek
+++ b/testing/btest/core/conn-uid.zeek
@@ -1,7 +1,7 @@
 #
 # In "normal" test mode, connection uids should be determistic.
 #
-# @TEST-EXEC: zeek -b -C -r $TRACES/wikipedia.trace %INPUT >output
+# @TEST-EXEC: zeek -b -D -C -r $TRACES/wikipedia.trace %INPUT >output
 # @TEST-EXEC: btest-diff output
 #
 # Without a seed, they should differ each time:
diff --git a/testing/btest/language/closure-binding-deprecated.zeek b/testing/btest/language/closure-binding-deprecated.zeek
new file mode 100644
index 0000000000..90a5c7e78f
--- /dev/null
+++ b/testing/btest/language/closure-binding-deprecated.zeek
@@ -0,0 +1,47 @@
+# @TEST-EXEC: zeek -b %INPUT >out
+# @TEST-EXEC: btest-diff out
+
+type mutable_aggregate: record { x: count; };
+
+function reference_capture() : function()
+	{
+	local a = 3;
+	local b = mutable_aggregate($x=11);
+	local f = function() { print ++a, --b$x; };
+	f();
+	++a;
+	--b$x;
+	f();
+
+	return f;
+	}
+
+function reference_capture_double() : function() : function()
+	{
+	local a = 3;
+	local b = mutable_aggregate($x=11);
+	local f = function() : function() {
+		local c = mutable_aggregate($x=88);
+		print ++a;
+		local f2 = function() { print a -= 2, --b$x, c$x += 3; };
+		c$x = c$x / 2;
+		return f2;
+		};
+	f()();
+	++a;
+	--b$x;
+	f()();
+
+	return f;
+	}
+
+event zeek_init()
+	{
+	print "reference capture";
+	local rc = reference_capture();
+	rc();
+
+	print "reference double capture";
+	local rc2 = reference_capture_double();
+	rc2()();
+	}
diff --git a/testing/btest/language/closure-binding.zeek b/testing/btest/language/closure-binding.zeek
index 6e1596b6f9..241c92484d 100644
--- a/testing/btest/language/closure-binding.zeek
+++ b/testing/btest/language/closure-binding.zeek
@@ -3,19 +3,6 @@
 
 type mutable_aggregate: record { x: count; };
 
-function reference_capture() : function()
-	{
-	local a = 3;
-	local b = mutable_aggregate($x=11);
-	local f = function() { print ++a, --b$x; };
-	f();
-	++a;
-	--b$x;
-	f();
-
-	return f;
-	}
-
 function shallow_copy_capture() : function()
 	{
 	local a = 3;
@@ -68,25 +55,6 @@ function mixed_copy_capture_b() : function()
 	return f;
 	}
 
-function reference_capture_double() : function() : function()
-	{
-	local a = 3;
-	local b = mutable_aggregate($x=11);
-	local f = function() : function() {
-		local c = mutable_aggregate($x=88);
-		print ++a;
-		local f2 = function() { print a -= 2, --b$x, c$x += 3; };
-		c$x = c$x / 2;
-		return f2;
-		};
-	f()();
-	++a;
-	--b$x;
-	f()();
-
-	return f;
-	}
-
 function shallow_copy_capture_double() : function() : function()
 	{
 	local a = 3;
@@ -167,33 +135,35 @@ function deep_copy3_capture_double() : function() : function()
 
 event zeek_init()
 	{
-	local rc = reference_capture();
-	rc();
-
+	print "shallow copy";
 	local scc = shallow_copy_capture();
 	scc();
 
+	print "deep copy";
 	local dcc = deep_copy_capture();
 	dcc();
 
+	print "mixed copy, case 1";
 	local mcca = mixed_copy_capture_a();
 	mcca();
 
+	print "mixed copy, case 2";
 	local mccb = mixed_copy_capture_b();
 	mccb();
 
-	local rc2 = reference_capture_double();
-	rc2()();
-
+	print "double shallow copy";
 	local scc2 = shallow_copy_capture_double();
 	scc2()();
 
+	print "double deep copy, case 1";
 	local dcc2_1 = deep_copy1_capture_double();
 	dcc2_1()();
 
+	print "double deep copy, case 2";
 	local dcc2_2 = deep_copy2_capture_double();
 	dcc2_2()();
 
+	print "double deep copy, case 3";
 	local dcc2_3 = deep_copy3_capture_double();
 	dcc2_3()();
 	}
diff --git a/testing/btest/language/closure-sending.zeek b/testing/btest/language/closure-sending-deprecated.zeek
similarity index 96%
rename from testing/btest/language/closure-sending.zeek
rename to testing/btest/language/closure-sending-deprecated.zeek
index f5a3e44035..09f403fc9b 100644
--- a/testing/btest/language/closure-sending.zeek
+++ b/testing/btest/language/closure-sending-deprecated.zeek
@@ -1,7 +1,7 @@
 # @TEST-PORT: BROKER_PORT
 #
-# @TEST-EXEC: btest-bg-run recv "zeek -B broker -b ../recv.zeek >recv.out"
-# @TEST-EXEC: btest-bg-run send "zeek -B broker -b ../send.zeek >send.out"
+# @TEST-EXEC: btest-bg-run recv "zeek -D -B broker -b ../recv.zeek >recv.out"
+# @TEST-EXEC: btest-bg-run send "zeek -D -B broker -b ../send.zeek >send.out"
 #
 # @TEST-EXEC: btest-bg-wait 45
 # @TEST-EXEC: btest-diff recv/recv.out
diff --git a/testing/btest/language/closure-sending-naming.zeek b/testing/btest/language/closure-sending-naming.zeek
index 27bc367d6d..8244ae9577 100644
--- a/testing/btest/language/closure-sending-naming.zeek
+++ b/testing/btest/language/closure-sending-naming.zeek
@@ -1,7 +1,7 @@
 # @TEST-PORT: BROKER_PORT
 #
-# @TEST-EXEC: btest-bg-run recv "zeek -B broker -b ../recv.zeek >recv.out 2>recv.error"
-# @TEST-EXEC: btest-bg-run send "zeek -B broker -b ../send.zeek >send.out"
+# @TEST-EXEC: btest-bg-run recv "zeek -D -B broker -b ../recv.zeek >recv.out 2>recv.error"
+# @TEST-EXEC: btest-bg-run send "zeek -D -B broker -b ../send.zeek >send.out"
 #
 # @TEST-EXEC: btest-bg-wait 20
 # @TEST-EXEC: btest-diff recv/recv.error
diff --git a/testing/btest/language/closure-sending2.zeek b/testing/btest/language/closure-sending2.zeek
index c6a421a708..e447b8224c 100644
--- a/testing/btest/language/closure-sending2.zeek
+++ b/testing/btest/language/closure-sending2.zeek
@@ -1,7 +1,7 @@
 # @TEST-PORT: BROKER_PORT
 #
-# @TEST-EXEC: btest-bg-run recv "zeek -B broker -b ../recv.zeek >recv.out"
-# @TEST-EXEC: btest-bg-run send "zeek -B broker -b ../send.zeek >send.out"
+# @TEST-EXEC: btest-bg-run recv "zeek -D -B broker -b ../recv.zeek >recv.out"
+# @TEST-EXEC: btest-bg-run send "zeek -D -B broker -b ../send.zeek >send.out"
 #
 # @TEST-EXEC: btest-bg-wait 45
 # @TEST-EXEC: btest-diff recv/recv.out
diff --git a/testing/btest/language/function-sending.zeek b/testing/btest/language/function-sending.zeek
index a45911878a..234e0a5431 100644
--- a/testing/btest/language/function-sending.zeek
+++ b/testing/btest/language/function-sending.zeek
@@ -1,7 +1,7 @@
 # @TEST-PORT: BROKER_PORT
 #
-# @TEST-EXEC: btest-bg-run recv "zeek -B broker -b ../recv.zeek >recv.out"
-# @TEST-EXEC: btest-bg-run send "zeek -B broker -b ../send.zeek >send.out"
+# @TEST-EXEC: btest-bg-run recv "zeek -D -B broker -b ../recv.zeek >recv.out"
+# @TEST-EXEC: btest-bg-run send "zeek -D -B broker -b ../send.zeek >send.out"
 #
 # @TEST-EXEC: btest-bg-wait 20
 # @TEST-EXEC: btest-diff recv/recv.out
diff --git a/testing/btest/language/paraglob-serialization.zeek b/testing/btest/language/paraglob-serialization.zeek
index c5d5d516dd..788aa4e95f 100644
--- a/testing/btest/language/paraglob-serialization.zeek
+++ b/testing/btest/language/paraglob-serialization.zeek
@@ -1,7 +1,7 @@
 # @TEST-PORT: BROKER_PORT
 #
-# @TEST-EXEC: btest-bg-run recv "zeek -B broker -b ../recv.zeek >recv.out"
-# @TEST-EXEC: btest-bg-run send "zeek -B broker -b ../send.zeek >send.out"
+# @TEST-EXEC: btest-bg-run recv "zeek -D -B broker -b ../recv.zeek >recv.out"
+# @TEST-EXEC: btest-bg-run send "zeek -D -B broker -b ../send.zeek >send.out"
 #
 # @TEST-EXEC: btest-bg-wait 45
 # @TEST-EXEC: btest-diff recv/recv.out
diff --git a/testing/btest/language/uninitialized-local3.zeek b/testing/btest/language/uninitialized-local3.zeek
index b251960633..f3aae38f5b 100644
--- a/testing/btest/language/uninitialized-local3.zeek
+++ b/testing/btest/language/uninitialized-local3.zeek
@@ -30,5 +30,13 @@ event zeek_init()
 	print x3;
 
 	local x4: count;
-	print x4;	# note, no execution after this point due to error
+	# note, no execution after this point due to error
+
+	# We use this slightly baroque expression because compiled code
+	# may have x4 genuinely uninitialized, and we want deterministic
+	# output in that case.
+	if ( x4 > 5 )
+		print T;
+	else
+		print T;
 	}