diff --git a/matrix.h b/matrix.h
index 6cf95ae..c91f512 100644
--- a/matrix.h
+++ b/matrix.h
@@ -7,7 +7,7 @@ typedef float MatrixType;
 
 typedef struct
 {
-    MatrixType **data;
+    MatrixType *buffer;
     unsigned int rows;
     unsigned int cols;
 } Matrix;
diff --git a/neuralNetwork.h b/neuralNetwork.h
index 7f06607..599bc04 100644
--- a/neuralNetwork.h
+++ b/neuralNetwork.h
@@ -1,9 +1,15 @@
 #ifndef NEURALNETWORK_H
 #define NEURALNETWORK_H
 
+#define checkFileHeader image_input_check_file_header_guard
+#define readDimension image_input_read_dimension_guard
 #include "imageInput.h"
+#undef checkFileHeader
+#undef readDimension
 #include "matrix.h"
 
+#define NEURAL_NETWORK_FILE_HEADER "__info2_neural_network_file_format__"
+
 typedef void (*ActivationFunctionType)(Matrix *X);
 
 typedef struct
diff --git a/neuralNetworkTests.c b/neuralNetworkTests.c
index 21ab370..9fb1e98 100644
--- a/neuralNetworkTests.c
+++ b/neuralNetworkTests.c
@@ -6,9 +6,56 @@
 #include "neuralNetwork.h"
 
 
-static void prepareNeuralNetworkFile(const char *path, const NeuralNetwork nn)
+static void writeDimension(FILE *file, unsigned int value)
 {
-    // TODO
+    const int serializedValue = (int)value;
+
+    TEST_ASSERT_EQUAL_size_t(1, fwrite(&serializedValue, sizeof(serializedValue), 1, file));
+}
+
+static void writeMatrix(FILE *file, const Matrix matrix) // writes all matrix elements in order
+{
+    const size_t elementCount = matrix.rows * matrix.cols;
+
+    TEST_ASSERT_EQUAL_size_t(elementCount, fwrite(matrix.buffer, sizeof(MatrixType), elementCount, file));
+}
+
+static void prepareNeuralNetworkFile(const char *path, const NeuralNetwork model)
+{
+    FILE *file = fopen(path, "wb");
+    TEST_ASSERT_NOT_NULL(file);
+
+    //writes header
+    const size_t headerLen = strlen(NEURAL_NETWORK_FILE_HEADER);
+    TEST_ASSERT_EQUAL_size_t(headerLen, fwrite(NEURAL_NETWORK_FILE_HEADER, sizeof(char), headerLen, file));
+
+    if(model.numberOfLayers == 0)
+    {
+        // sends 0 to loadModel so it terminates
+        writeDimension(file, 0);
+        writeDimension(file, 0);
+        fclose(file);
+        return;
+    }
+
+    // writes first layer
+    writeDimension(file, model.layers[0].weights.cols);
+    writeDimension(file, model.layers[0].weights.rows);
+
+    for(unsigned int layerCount = 0; layerCount < model.numberOfLayers; layerCount++) // write all other layers
+    {
+        const Layer layer = model.layers[layerCount];
+
+        writeMatrix(file, layer.weights);
+        writeMatrix(file, layer.biases);
+
+        const unsigned int nextOutput = (layerCount + 1 < model.numberOfLayers) //checks if there is another layer
+                                        ? model.layers[layerCount + 1].weights.rows
+                                        : 0;
+        writeDimension(file, nextOutput); // if 0 recieved loadModel() will terminate
+    }
+
+    fclose(file);
 }
 
 void test_loadModelReturnsCorrectNumberOfLayers(void)