diff --git a/include/kunit/kunit-stream.h b/include/kunit/kunit-stream.h
new file mode 100644
index 0000000000000..d457a54fe0100
--- /dev/null
+++ b/include/kunit/kunit-stream.h
@@ -0,0 +1,85 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/*
+ * C++ stream style string formatter and printer used in KUnit for outputting
+ * KUnit messages.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#ifndef _KUNIT_KUNIT_STREAM_H
+#define _KUNIT_KUNIT_STREAM_H
+
+#include <linux/types.h>
+#include <kunit/string-stream.h>
+
+struct kunit;
+
+/**
+ * struct kunit_stream - a std::stream style string builder.
+ *
+ * A std::stream style string builder. Allows messages to be built up and
+ * printed all at once.
+ */
+struct kunit_stream {
+	/* private: internal use only. */
+	struct kunit *test;
+	spinlock_t lock; /* Guards level. */
+	const char *level;
+	struct string_stream *internal_stream;
+};
+
+/**
+ * kunit_new_stream() - constructs a new &struct kunit_stream.
+ * @test: The test context object.
+ *
+ * Constructs a new test managed &struct kunit_stream.
+ */
+struct kunit_stream *kunit_new_stream(struct kunit *test);
+
+/**
+ * kunit_stream_set_level(): sets the level that string should be printed at.
+ * @this: the stream being operated on.
+ * @level: the print level the stream is set to output to.
+ *
+ * Sets the print level at which the stream outputs.
+ */
+void kunit_stream_set_level(struct kunit_stream *this, const char *level);
+
+/**
+ * kunit_stream_add(): adds the formatted input to the internal buffer.
+ * @this: the stream being operated on.
+ * @fmt: printf style format string to append to stream.
+ *
+ * Appends the formatted string, @fmt, to the internal buffer.
+ */
+void __printf(2, 3) kunit_stream_add(struct kunit_stream *this,
+				     const char *fmt, ...);
+
+/**
+ * kunit_stream_append(): appends the contents of @other to @this.
+ * @this: the stream to which @other is appended.
+ * @other: the stream whose contents are appended to @this.
+ *
+ * Appends the contents of @other to @this.
+ */
+void kunit_stream_append(struct kunit_stream *this, struct kunit_stream *other);
+
+/**
+ * kunit_stream_commit(): prints out the internal buffer to the user.
+ * @this: the stream being operated on.
+ *
+ * Outputs the contents of the internal buffer as a kunit_printk formatted
+ * output.
+ */
+void kunit_stream_commit(struct kunit_stream *this);
+
+/**
+ * kunit_stream_clear(): clears the internal buffer.
+ * @this: the stream being operated on.
+ *
+ * Clears the contents of the internal buffer.
+ */
+void kunit_stream_clear(struct kunit_stream *this);
+
+#endif /* _KUNIT_KUNIT_STREAM_H */
diff --git a/include/kunit/test.h b/include/kunit/test.h
index 819edd8db4e81..4668e8a635954 100644
--- a/include/kunit/test.h
+++ b/include/kunit/test.h
@@ -11,6 +11,7 @@
 
 #include <linux/types.h>
 #include <linux/slab.h>
+#include <kunit/kunit-stream.h>
 
 struct kunit_resource;
 
@@ -171,6 +172,7 @@ struct kunit {
 	void (*vprintk)(const struct kunit *test,
 			const char *level,
 			struct va_format *vaf);
+	void (*fail)(struct kunit *test, struct kunit_stream *stream);
 };
 
 int kunit_init_test(struct kunit *test, const char *name);
diff --git a/kunit/Makefile b/kunit/Makefile
index 275b565a0e81f..6ddc622ee6b1c 100644
--- a/kunit/Makefile
+++ b/kunit/Makefile
@@ -1,2 +1,3 @@
 obj-$(CONFIG_KUNIT) +=			test.o \
-					string-stream.o
+					string-stream.o \
+					kunit-stream.o
diff --git a/kunit/kunit-stream.c b/kunit/kunit-stream.c
new file mode 100644
index 0000000000000..93c14eec03844
--- /dev/null
+++ b/kunit/kunit-stream.c
@@ -0,0 +1,149 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * C++ stream style string formatter and printer used in KUnit for outputting
+ * KUnit messages.
+ *
+ * Copyright (C) 2019, Google LLC.
+ * Author: Brendan Higgins <brendanhiggins@google.com>
+ */
+
+#include <kunit/test.h>
+#include <kunit/kunit-stream.h>
+#include <kunit/string-stream.h>
+
+const char *kunit_stream_get_level(struct kunit_stream *this)
+{
+	unsigned long flags;
+	const char *level;
+
+	spin_lock_irqsave(&this->lock, flags);
+	level = this->level;
+	spin_unlock_irqrestore(&this->lock, flags);
+
+	return level;
+}
+
+void kunit_stream_set_level(struct kunit_stream *this, const char *level)
+{
+	unsigned long flags;
+
+	spin_lock_irqsave(&this->lock, flags);
+	this->level = level;
+	spin_unlock_irqrestore(&this->lock, flags);
+}
+
+void kunit_stream_add(struct kunit_stream *this, const char *fmt, ...)
+{
+	va_list args;
+	struct string_stream *stream = this->internal_stream;
+
+	va_start(args, fmt);
+
+	if (string_stream_vadd(stream, fmt, args) < 0)
+		kunit_err(this->test, "Failed to allocate fragment: %s\n", fmt);
+
+	va_end(args);
+}
+
+void kunit_stream_append(struct kunit_stream *this,
+				struct kunit_stream *other)
+{
+	struct string_stream *other_stream = other->internal_stream;
+	const char *other_content;
+
+	other_content = string_stream_get_string(other_stream);
+
+	if (!other_content) {
+		kunit_err(this->test,
+			  "Failed to get string from second argument for appending.\n");
+		return;
+	}
+
+	kunit_stream_add(this, other_content);
+}
+
+void kunit_stream_clear(struct kunit_stream *this)
+{
+	string_stream_clear(this->internal_stream);
+}
+
+void kunit_stream_commit(struct kunit_stream *this)
+{
+	struct string_stream *stream = this->internal_stream;
+	struct string_stream_fragment *fragment;
+	const char *level;
+	char *buf;
+
+	level = kunit_stream_get_level(this);
+	if (!level) {
+		kunit_err(this->test,
+			  "Stream was committed without a specified log level.\n");
+		level = KERN_ERR;
+		kunit_stream_set_level(this, level);
+	}
+
+	buf = string_stream_get_string(stream);
+	if (!buf) {
+		kunit_err(this->test,
+			 "Could not allocate buffer, dumping stream:\n");
+		list_for_each_entry(fragment, &stream->fragments, node) {
+			kunit_err(this->test, fragment->fragment);
+		}
+		kunit_err(this->test, "\n");
+		goto cleanup;
+	}
+
+	kunit_printk(level, this->test, buf);
+	kfree(buf);
+
+cleanup:
+	kunit_stream_clear(this);
+}
+
+static int kunit_stream_init(struct kunit_resource *res, void *context)
+{
+	struct kunit *test = context;
+	struct kunit_stream *stream;
+
+	stream = kzalloc(sizeof(*stream), GFP_KERNEL);
+	if (!stream)
+		return -ENOMEM;
+	res->allocation = stream;
+	stream->test = test;
+	spin_lock_init(&stream->lock);
+	stream->internal_stream = new_string_stream();
+
+	if (!stream->internal_stream)
+		return -ENOMEM;
+
+	return 0;
+}
+
+static void kunit_stream_free(struct kunit_resource *res)
+{
+	struct kunit_stream *stream = res->allocation;
+
+	if (!string_stream_is_empty(stream->internal_stream)) {
+		kunit_err(stream->test,
+			 "End of test case reached with uncommitted stream entries.\n");
+		kunit_stream_commit(stream);
+	}
+
+	destroy_string_stream(stream->internal_stream);
+	kfree(stream);
+}
+
+struct kunit_stream *kunit_new_stream(struct kunit *test)
+{
+	struct kunit_resource *res;
+
+	res = kunit_alloc_resource(test,
+				   kunit_stream_init,
+				   kunit_stream_free,
+				   test);
+
+	if (res)
+		return res->allocation;
+	else
+		return NULL;
+}
diff --git a/kunit/test.c b/kunit/test.c
index 541f9adb1608c..f7575b127e2df 100644
--- a/kunit/test.c
+++ b/kunit/test.c
@@ -63,12 +63,20 @@ static void kunit_vprintk(const struct kunit *test,
 			  "kunit %s: %pV", test->name, vaf);
 }
 
+static void kunit_fail(struct kunit *test, struct kunit_stream *stream)
+{
+	kunit_set_success(test, false);
+	kunit_stream_set_level(stream, KERN_ERR);
+	kunit_stream_commit(stream);
+}
+
 int kunit_init_test(struct kunit *test, const char *name)
 {
 	spin_lock_init(&test->lock);
 	INIT_LIST_HEAD(&test->resources);
 	test->name = name;
 	test->vprintk = kunit_vprintk;
+	test->fail = kunit_fail;
 
 	return 0;
 }
