diff --git a/src/context.cc b/src/context.cc
index bf6a0c05..465cd6ed 100644
--- a/src/context.cc
+++ b/src/context.cc
@@ -69,29 +69,45 @@ Context::~Context()
 	if (!parent) delete this->ctx_stack;
 }
 
-/*!
-	Initialize context from a module argument list and a evaluation context
-	which may pass variables which will be preferred over default values.
-*/
-void Context::setVariables(const AssignmentList &args,
-													 const EvalContext *evalctx)
+const Context::Expressions Context::getExpressions(const AssignmentList &args, const EvalContext *evalctx)
 {
+	Expressions expressions;
+
 	for(const auto &arg : args) {
-		set_variable(arg.name, arg.expr ? arg.expr->evaluate(this->parent) : ValuePtr::undefined);
+		expressions[arg.name] = arg.expr.get(); // NOTE: this can assign NULL pointers!
 	}
 
 	if (evalctx) {
 		size_t posarg = 0;
 		for (size_t i=0; i<evalctx->numArgs(); i++) {
 			const std::string &name = evalctx->getArgName(i);
-			ValuePtr val = evalctx->getArgValue(i);
+			const Expression *expr = evalctx->getArgs()[i].expr.get();
 			if (name.empty()) {
-				if (posarg < args.size()) this->set_variable(args[posarg++].name, val);
+				if (posarg < args.size()) {
+					const Assignment assignment = args[posarg++];
+					expressions[assignment.name] = expr;
+				}
 			} else {
-				this->set_variable(name, val);
+				expressions[name] = expr;
 			}
 		}
 	}
+
+	return expressions;
+}
+
+/*!
+	Initialize context from a module argument list and a evaluation context
+	which may pass variables which will be preferred over default values.
+*/
+const Context::Expressions Context::setVariables(const AssignmentList &args, const EvalContext *evalctx)
+{
+	const Expressions expressions = getExpressions(args, evalctx);
+	for (const auto &expr : expressions) {
+		const ValuePtr val = expr.second ? expr.second->evaluate(evalctx) : ValuePtr::undefined;
+		this->set_variable(expr.first, val);
+	}
+	return expressions;
 }
 
 void Context::set_variable(const std::string &name, const ValuePtr &value)
diff --git a/src/context.h b/src/context.h
index f9783409..18cc63b7 100644
--- a/src/context.h
+++ b/src/context.h
@@ -1,5 +1,6 @@
 #pragma once
 
+#include <map>
 #include <string>
 #include <vector>
 #include <unordered_map>
@@ -11,6 +12,8 @@ class Context
 {
 public:
 	typedef std::vector<const Context*> Stack;
+	typedef std::map<std::string, const class Expression *> Expressions;
+
 	Context(const Context *parent = NULL);
 	virtual ~Context();
 
@@ -18,15 +21,15 @@ public:
 	virtual ValuePtr evaluate_function(const std::string &name, const class EvalContext *evalctx) const;
 	virtual class AbstractNode *instantiate_module(const class ModuleInstantiation &inst, EvalContext *evalctx) const;
 
-	void setVariables(const AssignmentList &args,
-										const class EvalContext *evalctx = NULL);
+	const Expressions getExpressions(const AssignmentList &args, const class EvalContext *evalctx);
+	const Expressions setVariables(const AssignmentList &args, const class EvalContext *evalctx = NULL);
 
 	void set_variable(const std::string &name, const ValuePtr &value);
 	void set_variable(const std::string &name, const Value &value);
 	void set_constant(const std::string &name, const ValuePtr &value);
 	void set_constant(const std::string &name, const Value &value);
 
-        void apply_variables(const Context &other);
+	void apply_variables(const Context &other);
 	ValuePtr lookup_variable(const std::string &name, bool silent = false) const;
 	bool has_local_variable(const std::string &name) const;
 
diff --git a/src/control.cc b/src/control.cc
index 6fcb2680..f76e3a25 100644
--- a/src/control.cc
+++ b/src/control.cc
@@ -42,6 +42,7 @@ public: // types
 		CHILD,
 		CHILDREN,
 		ECHO,
+		ASSERT,
 		ASSIGN,
 		FOR,
 		LET,
@@ -49,9 +50,9 @@ public: // types
 		IF
     };
 public: // methods
-	ControlModule(Type type)
-		: type(type)
-	{ }
+	ControlModule(Type type) : type(type) { }
+
+	ControlModule(Type type, const Feature& feature) : AbstractModule(feature), type(type) { }
 
 	virtual AbstractNode *instantiate(const Context *ctx, const ModuleInstantiation *inst, EvalContext *evalctx) const;
 
@@ -276,6 +277,16 @@ AbstractNode *ControlModule::instantiate(const Context* /*ctx*/, const ModuleIns
 	}
 		break;
 
+	case ASSERT: {
+		node = new GroupNode(inst);
+
+		Context c(evalctx);
+		evaluate_assert(c, evalctx, inst->location());
+		inst->scope.apply(c);
+		node->children = inst->instantiateChildren(&c);
+	}
+		break;
+
 	case LET: {
 		node = new GroupNode(inst);
 		Context c(evalctx);
@@ -338,6 +349,7 @@ void register_builtin_control()
 	Builtins::init("child", new ControlModule(ControlModule::CHILD));
 	Builtins::init("children", new ControlModule(ControlModule::CHILDREN));
 	Builtins::init("echo", new ControlModule(ControlModule::ECHO));
+	Builtins::init("assert", new ControlModule(ControlModule::ASSERT, Feature::ExperimentalAssertExpression));
 	Builtins::init("assign", new ControlModule(ControlModule::ASSIGN));
 	Builtins::init("for", new ControlModule(ControlModule::FOR));
 	Builtins::init("let", new ControlModule(ControlModule::LET));
diff --git a/src/evalcontext.h b/src/evalcontext.h
index 08b499df..09f89d2c 100644
--- a/src/evalcontext.h
+++ b/src/evalcontext.h
@@ -19,6 +19,7 @@ public:
 	size_t numArgs() const { return this->eval_arguments.size(); }
 	const std::string &getArgName(size_t i) const;
 	ValuePtr getArgValue(size_t i, const Context *ctx = NULL) const;
+	const AssignmentList & getArgs() const { return this->eval_arguments; }
 
 	size_t numChildren() const;
 	ModuleInstantiation *getChild(size_t i) const;
diff --git a/src/exceptions.h b/src/exceptions.h
index 8cf58f41..c90024cd 100644
--- a/src/exceptions.h
+++ b/src/exceptions.h
@@ -9,6 +9,12 @@ public:
 	virtual ~EvaluationException() throw() {}
 };
 
+class AssertionFailedException : public EvaluationException {
+public:
+	AssertionFailedException(const std::string &what_arg) : EvaluationException(what_arg) {}
+	virtual ~AssertionFailedException() throw() {}
+};
+
 class RecursionException: public EvaluationException {
 public:
 	static RecursionException create(const char *recursiontype, const std::string &name) {
diff --git a/src/expr.cc b/src/expr.cc
index 45c568ea..62baf9b6 100644
--- a/src/expr.cc
+++ b/src/expr.cc
@@ -36,6 +36,9 @@
 #include "feature.h"
 #include <boost/bind.hpp>
 
+#include <boost/assign/std/vector.hpp>
+using namespace boost::assign; // bring 'operator+=()' into scope
+
 // unnamed namespace
 namespace {
 	bool isListComprehension(const shared_ptr<Expression> &e) {
@@ -399,6 +402,40 @@ void FunctionCall::print(std::ostream &stream) const
 	stream << this->name << "(" << this->arguments << ")";
 }
 
+Expression * FunctionCall::create(const std::string &funcname, const AssignmentList &arglist, Expression *expr, const Location &loc)
+{
+	if (funcname == "assert" && Feature::ExperimentalAssertExpression.is_enabled()) {
+		return new Assert(arglist, expr, loc);
+	} else if (funcname == "let") {
+		return new Let(arglist, expr, loc);
+	}
+
+	// TODO: Generate error/warning if expr != 0?
+	return new FunctionCall(funcname, arglist, loc);
+}
+
+Assert::Assert(const AssignmentList &args, Expression *expr, const Location &loc)
+	: Expression(loc), arguments(args), expr(expr)
+{
+
+}
+
+ValuePtr Assert::evaluate(const Context *context) const
+{
+	EvalContext assert_context(context, this->arguments);
+
+	Context c(&assert_context);
+	evaluate_assert(c, &assert_context, loc);
+
+	ValuePtr result = expr ? expr->evaluate(&c) : ValuePtr::undefined;
+	return result;
+}
+
+void Assert::print(std::ostream &stream) const
+{
+	stream << "assert(" << this->arguments << ") " << *expr;
+}
+
 Let::Let(const AssignmentList &args, Expression *expr, const Location &loc)
 	: Expression(loc), arguments(args), expr(expr)
 {
@@ -612,3 +649,30 @@ std::ostream &operator<<(std::ostream &stream, const Expression &expr)
 	expr.print(stream);
 	return stream;
 }
+
+void evaluate_assert(const Context &context, const class EvalContext *evalctx, const Location &loc)
+{
+	ExperimentalFeatureException::check(Feature::ExperimentalAssertExpression);
+
+	AssignmentList args;
+	args += Assignment("condition"), Assignment("message");
+
+	Context c(&context);
+	const Context::Expressions expressions = c.setVariables(args, evalctx);
+	const ValuePtr condition = c.lookup_variable("condition");
+
+	if (!condition->toBool()) {
+		std::stringstream msg;
+		msg << "ERROR: Assertion";
+		const Expression *expr = expressions.at("condition");
+		if (expr) {
+			msg << " '" << *expr << "'";
+		}
+		msg << " failed, line " << loc.firstLine();
+		const ValuePtr message = c.lookup_variable("message", true);
+		if (message->isDefined()) {
+			msg << ": " << message->toEchoString();
+		}
+		throw AssertionFailedException(msg.str());
+	}
+}
\ No newline at end of file
diff --git a/src/expression.h b/src/expression.h
index 8b1e1ff4..3a41208c 100644
--- a/src/expression.h
+++ b/src/expression.h
@@ -154,11 +154,23 @@ public:
 	FunctionCall(const std::string &funcname, const AssignmentList &arglist, const Location &loc);
 	ValuePtr evaluate(const class Context *context) const;
 	virtual void print(std::ostream &stream) const;
+	static Expression * create(const std::string &funcname, const AssignmentList &arglist, Expression *expr, const Location &loc);
 public:
 	std::string name;
 	AssignmentList arguments;
 };
 
+class Assert : public Expression
+{
+public:
+	Assert(const AssignmentList &args, Expression *expr, const Location &loc);
+	ValuePtr evaluate(const class Context *context) const;
+	virtual void print(std::ostream &stream) const;
+private:
+	AssignmentList arguments;
+	shared_ptr<Expression> expr;
+};
+
 class Let : public Expression
 {
 public:
@@ -233,3 +245,5 @@ private:
 	AssignmentList arguments;
 	shared_ptr<Expression> expr;
 };
+
+void evaluate_assert(const Context &context, const class EvalContext *evalctx, const Location &loc);
\ No newline at end of file
diff --git a/src/feature.cc b/src/feature.cc
index 1f97190b..00285b69 100644
--- a/src/feature.cc
+++ b/src/feature.cc
@@ -19,6 +19,7 @@ Feature::list_t Feature::feature_list;
  * argument to enable the option and for saving the option value in GUI
  * context.
  */
+const Feature Feature::ExperimentalAssertExpression("assert", "Enable <code>assert</code>.");
 const Feature Feature::ExperimentalEachExpression("lc-each", "Enable <code>each</code> expression in list comprehensions.");
 const Feature Feature::ExperimentalElseExpression("lc-else", "Enable <code>else</code> expression in list comprehensions.");
 const Feature Feature::ExperimentalForCExpression("lc-for-c", "Enable C-style <code>for</code> expression in list comprehensions.");
diff --git a/src/feature.h b/src/feature.h
index 0e8b5742..1261d340 100644
--- a/src/feature.h
+++ b/src/feature.h
@@ -14,6 +14,7 @@ public:
 	typedef std::vector<Feature *> list_t;
 	typedef list_t::iterator iterator;
 
+	static const Feature ExperimentalAssertExpression;
         static const Feature ExperimentalEachExpression;
         static const Feature ExperimentalElseExpression;
         static const Feature ExperimentalForCExpression;
diff --git a/src/mainwin.cc b/src/mainwin.cc
index 1a03c511..436de1e9 100644
--- a/src/mainwin.cc
+++ b/src/mainwin.cc
@@ -92,6 +92,13 @@
 #include <QClipboard>
 #include <QDesktopWidget>
 
+#if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
+#include <QTextDocument>
+#define QT_HTML_ESCAPE(qstring) Qt::escape(qstring)
+#else
+#define QT_HTML_ESCAPE(qstring) (qstring).toHtmlEscaped()
+#endif
+
 #if (QT_VERSION < QT_VERSION_CHECK(5, 1, 0))
 // Set dummy for Qt versions that do not have QSaveFile
 #define QT_FILE_SAVE_CLASS QFile
@@ -2671,10 +2678,10 @@ void MainWindow::consoleOutput(const QString &msg)
 	QString qmsg;
 	if (msg.startsWith("WARNING:") || msg.startsWith("DEPRECATED:")) {
 		this->compileWarnings++;
-		qmsg = "<html><span style=\"color: black; background-color: #ffffb0;\">" + msg + "</span></html>\n";
+		qmsg = "<html><span style=\"color: black; background-color: #ffffb0;\">" + QT_HTML_ESCAPE(QString(msg)) + "</span></html>\n";
 	} else if (msg.startsWith("ERROR:")) {
 		this->compileErrors++;
-		qmsg = "<html><span style=\"color: black; background-color: #ffb0b0;\">" + msg + "</span></html>\n";
+		qmsg = "<html><span style=\"color: black; background-color: #ffb0b0;\">" + QT_HTML_ESCAPE(QString(msg)) + "</span></html>\n";
 	}
 	else {
 		qmsg = msg;
diff --git a/src/parser.y b/src/parser.y
index cb440fb3..ab3e9a59 100644
--- a/src/parser.y
+++ b/src/parser.y
@@ -105,7 +105,7 @@ fs::path parser_sourcefile;
 
 %token LE GE EQ NE AND OR
 
-%right LET
+%left HIGH_PRIO_LEFT
 
 %right '?' ':'
 
@@ -120,11 +120,14 @@ fs::path parser_sourcefile;
 %left '[' ']'
 %left '.'
 
+%left LOW_PRIO_LEFT
+
 %type <expr> expr
 %type <vec> vector_expr
 %type <expr> list_comprehension_elements
 %type <expr> list_comprehension_elements_p
 %type <expr> list_comprehension_elements_or_expr
+%type <expr> expr_or_empty
 
 %type <inst> module_instantiation
 %type <ifelse> if_statement
@@ -337,11 +340,6 @@ expr:
             {
               $$ = new Literal(ValuePtr($1), LOC(@$));
             }
-        | TOK_LET '(' arguments_call ')' expr %prec LET
-            {
-              $$ = new Let(*$3, $5, LOC(@$));
-              delete $3;
-            }
         | '[' expr ':' expr ']'
             {
               $$ = new Range($2, $4, LOC(@$));
@@ -434,14 +432,30 @@ expr:
             {
               $$ = new ArrayLookup($1, $3, LOC(@$));
             }
-        | TOK_ID '(' arguments_call ')'
+        | TOK_ID '(' arguments_call ')' expr_or_empty
             {
-              $$ = new FunctionCall($1, *$3, LOC(@$));
-              free($1);
-              delete $3;
-            }
+              $$ = FunctionCall::create($1, *$3, $5, LOC(@$));
+			  free($1);
+			  delete $3;
+			}
+		| TOK_LET '(' arguments_call ')' expr_or_empty
+            {
+				$$ = FunctionCall::create("let", *$3, $5, LOC(@$));
+				delete $3;
+			}
         ;
 
+expr_or_empty:
+		  %prec LOW_PRIO_LEFT
+		    {
+			    $$ = NULL;
+		    }
+		| expr %prec HIGH_PRIO_LEFT
+		    {
+			    $$ = $1;
+		    }
+		;
+
 list_comprehension_elements:
           /* The last set element may not be a "let" (as that would instead
              be parsed as an expression) */
diff --git a/src/value.cc b/src/value.cc
index 4cd21f35..9491b5cd 100644
--- a/src/value.cc
+++ b/src/value.cc
@@ -267,6 +267,15 @@ std::string Value::toString() const
   return boost::apply_visitor(tostring_visitor(), this->value);
 }
 
+std::string Value::toEchoString() const
+{
+	if (type() == Value::STRING) {
+		return std::string("\"") + toString() + '"';
+	} else {
+		return toString();
+	}
+}
+
 class chr_visitor : public boost::static_visitor<std::string> {
 public:
 	template <typename S> std::string operator()(const S &) const
diff --git a/src/value.h b/src/value.h
index da57371c..afa7aa5f 100644
--- a/src/value.h
+++ b/src/value.h
@@ -169,6 +169,7 @@ public:
   bool getFiniteDouble(double &v) const;
   bool toBool() const;
   std::string toString() const;
+  std::string toEchoString() const;
   std::string chrString() const;
   const VectorType &toVector() const;
   bool getVec2(double &x, double &y, bool ignoreInfinite = false) const;
diff --git a/testdata/scad/functions/assert-expression-fail1-test.scad b/testdata/scad/functions/assert-expression-fail1-test.scad
new file mode 100644
index 00000000..81dd6d72
--- /dev/null
+++ b/testdata/scad/functions/assert-expression-fail1-test.scad
@@ -0,0 +1,2 @@
+v = assert(false);
+echo(v);
diff --git a/testdata/scad/functions/assert-expression-fail2-test.scad b/testdata/scad/functions/assert-expression-fail2-test.scad
new file mode 100644
index 00000000..e363f443
--- /dev/null
+++ b/testdata/scad/functions/assert-expression-fail2-test.scad
@@ -0,0 +1,4 @@
+a = 10;
+b = 20;
+v = assert(a < 20 && b < 20, "Test! <html>&</html>");
+echo(v);
diff --git a/testdata/scad/functions/assert-expression-fail3-test.scad b/testdata/scad/functions/assert-expression-fail3-test.scad
new file mode 100644
index 00000000..fe9e0b44
--- /dev/null
+++ b/testdata/scad/functions/assert-expression-fail3-test.scad
@@ -0,0 +1,7 @@
+function f(x) = sin(x);
+
+module m(angle) {
+	v = assert(f(angle) > 0) 10;
+}
+
+m(270);
diff --git a/testdata/scad/functions/assert-expression-tests.scad b/testdata/scad/functions/assert-expression-tests.scad
new file mode 100644
index 00000000..cdf78295
--- /dev/null
+++ b/testdata/scad/functions/assert-expression-tests.scad
@@ -0,0 +1,25 @@
+a = 3;
+b = 6;
+
+t0 = assert(true);
+echo(t0 = t0);
+
+t1 = assert("t1");
+echo(t1 = t1);
+
+t2 = assert(a*b);
+echo(t2 = t2);
+
+t3 = assert(condition = a*b);
+echo(t3 = t3);
+
+t4 = assert(true) a*b;
+echo(t4 = t4);
+
+c = 2;
+t5 = assert(condition = 2) a*b*c;
+echo(t5 = t5);
+
+d = c + 9;
+t6 = assert(condition = d + 5 > 15, message = str("value: ", d + 5)) a*b*c*d;
+echo(t6 = t6);
diff --git a/testdata/scad/misc/assert-fail1-test.scad b/testdata/scad/misc/assert-fail1-test.scad
new file mode 100644
index 00000000..d8fc3ea0
--- /dev/null
+++ b/testdata/scad/misc/assert-fail1-test.scad
@@ -0,0 +1 @@
+assert(false);
\ No newline at end of file
diff --git a/testdata/scad/misc/assert-fail2-test.scad b/testdata/scad/misc/assert-fail2-test.scad
new file mode 100644
index 00000000..0db2fcdd
--- /dev/null
+++ b/testdata/scad/misc/assert-fail2-test.scad
@@ -0,0 +1,3 @@
+a = 10;
+b = 20;
+assert(a < 20 && b < 20, "Test! <html>&</html>");
diff --git a/testdata/scad/misc/assert-fail3-test.scad b/testdata/scad/misc/assert-fail3-test.scad
new file mode 100644
index 00000000..c0fdba10
--- /dev/null
+++ b/testdata/scad/misc/assert-fail3-test.scad
@@ -0,0 +1,7 @@
+function f(x) = sin(x);
+
+module m(angle) {
+	assert(f(angle) > 0) cube(10);
+}
+
+m(270);
diff --git a/testdata/scad/misc/assert-tests.scad b/testdata/scad/misc/assert-tests.scad
new file mode 100644
index 00000000..96703eb2
--- /dev/null
+++ b/testdata/scad/misc/assert-tests.scad
@@ -0,0 +1,24 @@
+a = 3;
+b = 6;
+
+assert(true);
+
+assert("t1");
+
+assert(a*b);
+
+assert(condition = a*b);
+
+assert(true) cube(8, center = true);
+
+c = 2;
+translate([0, 20, 0])
+assert(condition = 2)
+sphere(5);
+
+d = c + 9;
+assert(condition = d + 5 > 15, message = str("value: ", d + 5))
+translate([15, 0, 0])
+cylinder(8, 5, center = true);
+
+echo("assert-tests");
\ No newline at end of file
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index c921e515..01cb85ef 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -1032,7 +1032,7 @@ function(add_cmdline_test TESTCMD_BASENAME)
       if (${EXPERIMENTAL} EQUAL -1)
         set(EXPERIMENTAL_OPTION "")
       else()
-        set(EXPERIMENTAL_OPTION "--enable=lc-each" "--enable=lc-else" "--enable=lc-for-c")
+        set(EXPERIMENTAL_OPTION "--enable=assert" "--enable=lc-each" "--enable=lc-else" "--enable=lc-for-c")
       endif()
 
       # 2D tests should be viewed from the top, not an angle.
@@ -1161,6 +1161,10 @@ list(APPEND ECHO_FILES ${FUNCTION_FILES}
             ${CMAKE_SOURCE_DIR}/../testdata/scad/3D/features/for-tests.scad
             ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/expression-evaluation-tests.scad
             ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/echo-tests.scad
+            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-tests.scad
+            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-fail1-test.scad
+            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-fail2-test.scad
+            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-fail3-test.scad
             ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/escape-test.scad
             ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/parser-tests.scad
             ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/builtin-tests.scad
@@ -1205,6 +1209,7 @@ list(APPEND DUMPTEST_FILES ${FEATURES_2D_FILES} ${FEATURES_3D_FILES} ${DEPRECATE
 list(APPEND DUMPTEST_FILES ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/escape-test.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/include-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/use-tests.scad
+                           ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/let-module-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/localfiles-test.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/localfiles_dir/localfiles-compatibility-test.scad
@@ -1216,6 +1221,7 @@ list(APPEND CGALPNGTEST_2D_FILES ${FEATURES_2D_FILES} ${SCAD_DXF_FILES} ${EXAMPL
 list(APPEND CGALPNGTEST_3D_FILES ${FEATURES_3D_FILES} ${DEPRECATED_3D_FILES} ${ISSUES_3D_FILES} ${EXAMPLE_3D_FILES})
 list(APPEND CGALPNGTEST_3D_FILES ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/include-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/use-tests.scad
+                           ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/assert-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/let-module-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/bugs/transform-nan-inf-tests.scad
                            ${CMAKE_SOURCE_DIR}/../testdata/scad/misc/localfiles-test.scad
@@ -1350,7 +1356,20 @@ disable_tests(csgpngtest_primitive-inf-tests
               cgalpngtest_empty-shape-tests
               csgpngtest_issue1258)
 
-experimental_tests(echotest_list-comprehensions-experimental)
+experimental_tests(echotest_list-comprehensions-experimental
+                   echotest_assert-tests
+                   cgalpngtest_assert-tests
+                   opencsgtest_assert-tests
+                   csgpngtest_assert-tests
+                   throwntogethertest_assert-tests
+                   echotest_assert-fail1-test
+                   echotest_assert-fail2-test
+                   echotest_assert-fail3-test
+                   echotest_echo-expression-tests
+                   echotest_assert-expression-tests
+                   echotest_assert-expression-fail1-test
+                   echotest_assert-expression-fail2-test
+                   echotest_assert-expression-fail3-test)
 
 # Test config handling
 
diff --git a/tests/regression/cgalpngtest/assert-tests-expected.png b/tests/regression/cgalpngtest/assert-tests-expected.png
new file mode 100644
index 00000000..fc7c37f3
Binary files /dev/null and b/tests/regression/cgalpngtest/assert-tests-expected.png differ
diff --git a/tests/regression/dumptest/assert-tests-expected.csg b/tests/regression/dumptest/assert-tests-expected.csg
new file mode 100644
index 00000000..fb6a5306
--- /dev/null
+++ b/tests/regression/dumptest/assert-tests-expected.csg
@@ -0,0 +1,2 @@
+multmatrix([[1, 0, 0, 0], [0, 1, 0, 20], [0, 0, 1, 0], [0, 0, 0, 1]]);
+group();
diff --git a/tests/regression/echotest/assert-expression-fail1-test-expected.echo b/tests/regression/echotest/assert-expression-fail1-test-expected.echo
new file mode 100644
index 00000000..d093613f
--- /dev/null
+++ b/tests/regression/echotest/assert-expression-fail1-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion 'false' failed, line 1
diff --git a/tests/regression/echotest/assert-expression-fail2-test-expected.echo b/tests/regression/echotest/assert-expression-fail2-test-expected.echo
new file mode 100644
index 00000000..9c620f23
--- /dev/null
+++ b/tests/regression/echotest/assert-expression-fail2-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion '((a < 20) && (b < 20))' failed, line 3: "Test! <html>&</html>"
diff --git a/tests/regression/echotest/assert-expression-fail3-test-expected.echo b/tests/regression/echotest/assert-expression-fail3-test-expected.echo
new file mode 100644
index 00000000..1528c368
--- /dev/null
+++ b/tests/regression/echotest/assert-expression-fail3-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion '(f(angle) > 0)' failed, line 4
diff --git a/tests/regression/echotest/assert-expression-tests-expected.echo b/tests/regression/echotest/assert-expression-tests-expected.echo
new file mode 100644
index 00000000..f53c1512
--- /dev/null
+++ b/tests/regression/echotest/assert-expression-tests-expected.echo
@@ -0,0 +1,7 @@
+ECHO: t0 = undef
+ECHO: t1 = undef
+ECHO: t2 = undef
+ECHO: t3 = undef
+ECHO: t4 = 18
+ECHO: t5 = 36
+ECHO: t6 = 396
diff --git a/tests/regression/echotest/assert-fail1-test-expected.echo b/tests/regression/echotest/assert-fail1-test-expected.echo
new file mode 100644
index 00000000..d093613f
--- /dev/null
+++ b/tests/regression/echotest/assert-fail1-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion 'false' failed, line 1
diff --git a/tests/regression/echotest/assert-fail2-test-expected.echo b/tests/regression/echotest/assert-fail2-test-expected.echo
new file mode 100644
index 00000000..9c620f23
--- /dev/null
+++ b/tests/regression/echotest/assert-fail2-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion '((a < 20) && (b < 20))' failed, line 3: "Test! <html>&</html>"
diff --git a/tests/regression/echotest/assert-fail3-test-expected.echo b/tests/regression/echotest/assert-fail3-test-expected.echo
new file mode 100644
index 00000000..1528c368
--- /dev/null
+++ b/tests/regression/echotest/assert-fail3-test-expected.echo
@@ -0,0 +1 @@
+ERROR: Assertion '(f(angle) > 0)' failed, line 4
diff --git a/tests/regression/echotest/assert-tests-expected.echo b/tests/regression/echotest/assert-tests-expected.echo
new file mode 100644
index 00000000..228aabad
--- /dev/null
+++ b/tests/regression/echotest/assert-tests-expected.echo
@@ -0,0 +1 @@
+ECHO: "assert-tests"
diff --git a/tests/regression/opencsgtest/assert-tests-expected.png b/tests/regression/opencsgtest/assert-tests-expected.png
new file mode 100644
index 00000000..d33ffa8e
Binary files /dev/null and b/tests/regression/opencsgtest/assert-tests-expected.png differ
diff --git a/tests/regression/throwntogethertest/assert-tests-expected.png b/tests/regression/throwntogethertest/assert-tests-expected.png
new file mode 100644
index 00000000..c4c70d78
Binary files /dev/null and b/tests/regression/throwntogethertest/assert-tests-expected.png differ