diff --git a/server/src/core/folder-core.test.ts b/server/src/core/folder-core.test.ts
new file mode 100644
index 000000000..704c7a6ec
--- /dev/null
+++ b/server/src/core/folder-core.test.ts
@@ -0,0 +1,200 @@
+import t from "tap";
+import CreateLogCtx from "../logger";
+import { Testing511SPA } from "../test-utils/test-data";
+import { ChartDocument, FolderDocument } from "kamaitachi-common";
+import {
+    CreateFolderChartLookup,
+    GetFolderChartIDs,
+    GetFolderCharts,
+    ResolveFolderToCharts,
+} from "./folder-core";
+import db, { CloseMongoConnection } from "../db/db";
+import ResetDBState from "../test-utils/reset-db-state";
+import deepmerge from "deepmerge";
+
+const logger = CreateLogCtx("folder-core.test.ts");
+
+t.test("#ResolveFolderToCharts", (t) => {
+    t.beforeEach(ResetDBState);
+
+    t.test("Static Folder Tests", (t) => {
+        t.test("Basic Static", async (t) => {
+            let mockFolder = {
+                game: "iidx",
+                playtype: "SP",
+                type: "static",
+                data: [Testing511SPA.chartID],
+            };
+
+            let { charts } = await ResolveFolderToCharts(mockFolder as FolderDocument);
+
+            t.equal(charts.length, 1, "Should return exactly 1 chart.");
+            t.equal(charts[0].chartID, Testing511SPA.chartID, "Should return 511 [SPA]");
+
+            t.end();
+        });
+
+        t.test("Empty Static", async (t) => {
+            let mockFolder = {
+                game: "iidx",
+                playtype: "SP",
+                type: "static",
+                data: [],
+            };
+
+            let { charts } = await ResolveFolderToCharts((mockFolder as unknown) as FolderDocument);
+
+            t.equal(charts.length, 0, "Should return exactly 0 charts.");
+
+            t.end();
+        });
+
+        t.end();
+    });
+
+    t.test("Songs Folder Tests", (t) => {
+        t.test("Basic Song Query", async (t) => {
+            let mockFolder = {
+                game: "iidx",
+                playtype: "SP",
+                type: "songs",
+                data: {
+                    title: { $regex: /5\.1\.1/u },
+                },
+            };
+
+            let { charts } = await ResolveFolderToCharts(mockFolder as FolderDocument);
+
+            t.equal(charts.length, 1, "Should return exactly 1 chart.");
+            t.equal(charts[0].chartID, Testing511SPA.chartID, "Should return 511 [SPA]");
+            t.end();
+        });
+
+        t.test("Invalid Song Query", async (t) => {
+            let mockFolder = {
+                game: "iidx",
+                playtype: "SP",
+                type: "songs",
+                data: {
+                    FieldThatDoesntExist: { $regex: /5\.1\.1/u },
+                },
+            };
+
+            let { charts } = await ResolveFolderToCharts((mockFolder as unknown) as FolderDocument);
+
+            t.equal(charts.length, 0, "Should return exactly 0 charts.");
+            t.end();
+        });
+
+        t.end();
+    });
+
+    t.test("Charts Folder Tests", (t) => {
+        t.test("Basic Song Query", async (t) => {
+            let mockFolder = {
+                game: "iidx",
+                playtype: "SP",
+                type: "charts",
+                data: {
+                    songID: Testing511SPA.songID, // lol
+                },
+            };
+
+            let { charts } = await ResolveFolderToCharts(mockFolder as FolderDocument);
+
+            t.equal(charts.length, 1, "Should return exactly 1 chart.");
+            t.equal(charts[0].chartID, Testing511SPA.chartID, "Should return 511 [SPA]");
+            t.end();
+        });
+
+        t.end();
+    });
+
+    t.test("Filter", async (t) => {
+        // add fake "NORMAL" 511 chart
+        await db.charts.iidx.insert(
+            deepmerge(Testing511SPA, {
+                difficulty: "NORMAL",
+                chartID: "FAKE_511_SPN",
+            }) as ChartDocument<"iidx:SP">
+        );
+
+        let mockFolder = {
+            game: "iidx",
+            playtype: "SP",
+            type: "charts",
+            data: {
+                songID: Testing511SPA.songID, // lol
+            },
+        };
+
+        let { charts } = await ResolveFolderToCharts(mockFolder as FolderDocument);
+
+        t.equal(charts.length, 2, "Should return exactly 2 charts.");
+        t.strictSame(
+            charts.map((e) => e.chartID),
+            [Testing511SPA.chartID, "FAKE_511_SPN"],
+            "Should return all 511 charts."
+        );
+
+        let { charts: charts2 } = await ResolveFolderToCharts(mockFolder as FolderDocument, {
+            difficulty: "NORMAL",
+        });
+
+        t.equal(charts2.length, 1, "Should return exactly 1 chart.");
+        t.equal(charts2[0].chartID, "FAKE_511_SPN", "Should only return 511 SPN");
+
+        t.end();
+    });
+
+    t.test("Songs", async (t) => {
+        let mockFolder = {
+            game: "iidx",
+            playtype: "SP",
+            type: "charts",
+            data: {
+                songID: Testing511SPA.songID, // lol
+            },
+        };
+
+        let { charts, songs } = await ResolveFolderToCharts(mockFolder as FolderDocument, {}, true);
+
+        t.equal(charts.length, 1, "Should return exactly 1 chart.");
+        t.equal(charts[0].chartID, Testing511SPA.chartID, "Should return 511 [SPA]");
+
+        t.equal(songs.length, 1, "Should return exactly 1 song.");
+        t.equal(songs[0].id, Testing511SPA.songID, "Should return 511's song.");
+
+        t.end();
+    });
+
+    t.end();
+});
+
+t.test("#GetFolderChartIDs", (t) => {
+    t.beforeEach(ResetDBState);
+
+    t.test("Should use the folder-cache", async (t) => {
+        await db["folder-chart-lookup"].insert(
+            ["a", "b", "c", "d"].map((e) => ({ chartID: e, folderID: "folder1" }))
+        );
+
+        await db["folder-chart-lookup"].insert(
+            ["e", "f", "g", "h"].map((e) => ({ chartID: e, folderID: "folder2" }))
+        );
+
+        let fcIDs = await GetFolderChartIDs("folder1");
+
+        t.strictSame(fcIDs, ["a", "b", "c", "d"], "Should return the right chartIDs for folder1");
+
+        fcIDs = await GetFolderChartIDs("folder2");
+
+        t.strictSame(fcIDs, ["e", "f", "g", "h"], "Should return the right chartIDs for folder2");
+
+        t.end();
+    });
+
+    t.end();
+});
+
+t.teardown(CloseMongoConnection);