diff --git a/water/https_downloader_test.go b/water/https_downloader_test.go
new file mode 100644
index 00000000..68bfb631
--- /dev/null
+++ b/water/https_downloader_test.go
@@ -0,0 +1,90 @@
+package water
+
+import (
+	"bytes"
+	"context"
+	"io"
+	"net/http"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
+)
+
+type roundTripFunc struct {
+	f func(req *http.Request) (*http.Response, error)
+}
+
+func (f *roundTripFunc) RoundTrip(req *http.Request) (*http.Response, error) {
+	return f.f(req)
+}
+
+func TestHTTPSDownloadWASM(t *testing.T) {
+	ctx := context.Background()
+	var tests = []struct {
+		name            string
+		givenHTTPClient *http.Client
+		givenURL        string
+		assert          func(*testing.T, io.Reader, error)
+	}{
+		{
+			name: "sending request successfully",
+			givenHTTPClient: &http.Client{
+				Transport: &roundTripFunc{
+					f: func(req *http.Request) (*http.Response, error) {
+						return &http.Response{
+							StatusCode: http.StatusOK,
+							Body:       io.NopCloser(bytes.NewBufferString("wasm")),
+						}, nil
+					},
+				},
+			},
+			givenURL: "https://example.com/wasm.wasm",
+			assert: func(t *testing.T, r io.Reader, err error) {
+				assert.NoError(t, err)
+				b, err := io.ReadAll(r)
+				require.NoError(t, err)
+				assert.Equal(t, "wasm", string(b))
+			},
+		},
+		{
+			name: "when receiving an error from the HTTP client, it should return an error",
+			givenHTTPClient: &http.Client{
+				Transport: &roundTripFunc{
+					f: func(req *http.Request) (*http.Response, error) {
+						return nil, assert.AnError
+					},
+				},
+			},
+			givenURL: "https://example.com/wasm.wasm",
+			assert: func(t *testing.T, r io.Reader, err error) {
+				assert.Error(t, err)
+				assert.Contains(t, err.Error(), "failed to send a HTTP request")
+			},
+		},
+		{
+			name: "when the HTTP status code is not 200, it should return an error",
+			givenHTTPClient: &http.Client{
+				Transport: &roundTripFunc{
+					f: func(req *http.Request) (*http.Response, error) {
+						return &http.Response{
+							StatusCode: http.StatusNotFound,
+						}, nil
+					},
+				},
+			},
+			givenURL: "https://example.com/wasm.wasm",
+			assert: func(t *testing.T, r io.Reader, err error) {
+				assert.Error(t, err)
+				assert.Contains(t, err.Error(), "failed to download WASM file")
+			},
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			b := new(bytes.Buffer)
+			err := NewHTTPSDownloader(tt.givenHTTPClient, tt.givenURL).DownloadWASM(ctx, b)
+			tt.assert(t, b, err)
+		})
+	}
+}